Originally posted by Isolde: Guru went off the deep end with cam selection, and is gaining more like an extra 1000 rpm over stock, about 1500 rpm over his old 350 combo.
My wife and friends would agree than I am certifiable on multiple fronts and prefer to take the hard way most of the time. I build my swaps to suit me and no one else. My old (and quite mild) SBC swap power band/dyno was very similar to most modified LS4 dyno's (through an auto) with my swap having slightly more wtq and whp due to a manual vs. auto... But while the performance was essentially the same, the LS4 is lighter, newer, more fuel efficient and has more potential... especially when coupled to a manual transmission. So if I am going to spend a year+ R&Ding a truly unique swap, I might as well give it an RPM band similar to a DOHC engine at the same time.
If it makes civic's cry who cares realy though does it matter as long as it goes fast and does what the owner wants, nope. In the end its a fiero and its the car that brought us all together. 3.4 3400, 3800, sbc, lsx and all swaps inbetween. Share in the fieroness and stop the swap hate.
IP: Logged
10:41 PM
May 17th, 2011
Adam1988 Member
Posts: 326 From: Tigard, Oregon, USA Registered: Jul 2007
A few other guys hit on some points that I agree with:
Outside of build threads/started projects, most SBC talk gets bashed - especially in the "Which should I go with..." type threads. Personally, I think all the engine swaps are pretty cool. Most of the guys in N.C. that I know of have 3800 variants swaps, they think my V8 is pretty cool and I think theirs are cool too.
CowsPatoot once told me he didn't care for the sound the SBC had, it didn't "fit" the Fiero. I agreed with him, but said I liked it for that same reason, it makes people go "WTF did you do...?" he also discovered the show factor when it comes to non-Fiero people. They see a really slick 3800 install - especially the ones where the owner went the extra mile to totally redo fuel lines and wires to make it look super-factory-ish, and they go "oh, that's cool, you did a nifty job." they don't really realize or appreciate the work/art that went into it. But then there's times when you pull in someplace (like CP went to an autozone with mine), and the place cleared out to check it out with a lot of "Holy ****! There's a 350 in there!"
I stuck with the V8 because mine came with a V8, and I love V8 engines to begin with. I love putting out tons of power N/A. I think Tim mentioned earlier about how most people don't want their cars to crank out more than 400 HP, or if they do, they don't understand what they're getting into. I've been in high power, light weight cars, so I knew I wanted a monster - even made it a point with my builder that I was more concerned on the HP than the Torque, since the car was so light. So that was taken into consideration with cam selection.
Now in hindsight, since I knew I eventually wanted to go EFI, if I could have found people local that I trusted to the extra work, I probably would have gone with a forged crate LSx and had a blast, and as someone else mentioned, the LSx engines are just SBC with a few small changes.
As for mileage - don't really care, it's my fun car, not my DD.
As for cost - don't really care, getting what I wanted was the goal, if I was worried about cost, I'd go buy the cheapest, tiniest car I could find that was reliable and not mess with it!.
As for being/not being "better" than another swap - again, I got what I wanted, and I'm very happy with it, all things considered. And being happy with what you got is the point.
The only thing that bugs me, and I plan on fixing, is that to drop the cradle/engine, I need to take off my electric water pump. So I'll have to bump up and get one of those remote mountable ones at some point.
Another reason I keep quiet is because... well, I'm an amateur. I openly admit that beyond the basics (changing the oil, spark plugs/wires and filling the cooling system, change brake pads/rotors), I'm a dummy when it comes to Fiero stuff, and I'm usually too worried that I'm going to seriously break something major to experiment/learn on my own without help/observation. I am one of those guys that would gladly pay someone to get things done, and I'll be happy to assist/be a tool gopher, and I always do my best to give credit where it's due.
A few other guys hit on some points that I agree with:
Outside of build threads/started projects, most SBC talk gets bashed - especially in the "Which should I go with..." type threads. Personally, I think all the engine swaps are pretty cool. Most of the guys in N.C. that I know of have 3800 variants swaps, they think my V8 is pretty cool and I think theirs are cool too.
CowsPatoot once told me he didn't care for the sound the SBC had, it didn't "fit" the Fiero. I agreed with him, but said I liked it for that same reason, it makes people go "WTF did you do...?" he also discovered the show factor when it comes to non-Fiero people. They see a really slick 3800 install - especially the ones where the owner went the extra mile to totally redo fuel lines and wires to make it look super-factory-ish, and they go "oh, that's cool, you did a nifty job." they don't really realize or appreciate the work/art that went into it. But then there's times when you pull in someplace (like CP went to an autozone with mine), and the place cleared out to check it out with a lot of "Holy ****! There's a 350 in there!"
I stuck with the V8 because mine came with a V8, and I love V8 engines to begin with. I love putting out tons of power N/A. I think Tim mentioned earlier about how most people don't want their cars to crank out more than 400 HP, or if they do, they don't understand what they're getting into. I've been in high power, light weight cars, so I knew I wanted a monster - even made it a point with my builder that I was more concerned on the HP than the Torque, since the car was so light. So that was taken into consideration with cam selection.
Now in hindsight, since I knew I eventually wanted to go EFI, if I could have found people local that I trusted to the extra work, I probably would have gone with a forged crate LSx and had a blast, and as someone else mentioned, the LSx engines are just SBC with a few small changes.
As for mileage - don't really care, it's my fun car, not my DD.
As for cost - don't really care, getting what I wanted was the goal, if I was worried about cost, I'd go buy the cheapest, tiniest car I could find that was reliable and not mess with it!.
As for being/not being "better" than another swap - again, I got what I wanted, and I'm very happy with it, all things considered. And being happy with what you got is the point.
The only thing that bugs me, and I plan on fixing, is that to drop the cradle/engine, I need to take off my electric water pump. So I'll have to bump up and get one of those remote mountable ones at some point.
Another reason I keep quiet is because... well, I'm an amateur. I openly admit that beyond the basics (changing the oil, spark plugs/wires and filling the cooling system, change brake pads/rotors), I'm a dummy when it comes to Fiero stuff, and I'm usually too worried that I'm going to seriously break something major to experiment/learn on my own without help/observation. I am one of those guys that would gladly pay someone to get things done, and I'll be happy to assist/be a tool gopher, and I always do my best to give credit where it's due.
Thanks for the great post Trinton, that pretty much sums up my reasoning... very, very well said.
My thoughts? I have never been into braggin' or talkin' sh!t to anyone about anything, whether it be in a public forum or real life. I've seen many "V8 vs. such-and-such a swap" threads over the years. Many become "junk" threads because of the personal insecurities that inevitably surface from someone that happens to have a different opinion about the swap. As my dad used to say "different strokes for different folks." The same concept applies here; you don't like the idea of an old-school SBC sitting in the back of a Fiero? That's ok, it really is... to each his own.
I am happy with my V8 Fiero... I love having gobs of torque and butt-loads of horsepower just a toe-twitch away... low-rpm street-grunt and wicked-fast acceleration on demand... yummm! Do I brag about my V8 Fiero, or even put down other Fiero owner's with different engine swaps? No, I do not and never will. It just doesn't make sense. Would I love a 3800SC Fiero? Yer damn right. LSX??? Oh HELL yeah. (name your swap here)???... props! I'm not picky. It's still a Fiero!
"Very little discussion on SBC V8 swaps lately... WHY?"
It's 2011... the Fiero is now about 27 years old. When it was first made, there were no 3800 swaps, no 3.4's, no V8's, etc... remember when Archie first started doing swaps? Yeah, that was a long time ago. I remember. Archie was told he couldn't fit a V8 in a Fiero... so he did it and proved to the nay-sayer's wrong, then made himself a legit business out of it. The result is that of legend... need I say more. The bottom line is that Fiero SBC swaps have been around for a LONG time. The swap is proven, whether done by Archie or Joe Schmoe's one-car garage. The swap works. Period.
Since then, we've seen massive leaps in technology and innovation... smaller engines (and even GM's LS V8's) are making more horsepower/torque and getting better gas mileage. Seems only natural that one would consider transplanting one of these new-generation, highly-efficient power-plants into our humble Fiero. THAT'S why I think there are less SBC swap threads. At least, that's my take anyways... =)
Brett
[This message has been edited by ITALGT (edited 05-18-2011).]
IP: Logged
01:30 AM
blackrams Member
Posts: 32792 From: Covington, TN, USA Registered: Feb 2003
My wife and friends would agree than I am certifiable on multiple fronts and prefer to take the hard way most of the time. I build my swaps to suit me and no one else.
Spoken as truth. But Paul is also one of the most talented engineers/builders I've ever met. This guy's mind never stops mulling over better ways to do things. I only wish I had half his talent.
quote
Originally posted by fieroguru:
My old (and quite mild) SBC swap power band/dyno was very similar to most modified LS4 dyno's (through an auto) with my swap having slightly more wtq and whp due to a manual vs. auto... But while the performance was essentially the same, the LS4 is lighter, newer, more fuel efficient and has more potential... especially when coupled to a manual transmission. So if I am going to spend a year+ R&Ding a truly unique swap, I might as well give it an RPM band similar to a DOHC engine at the same time.
Mild, yeah right. That SBC was long on power and very cool in the way Paul put it together. A very impressive ride. His latest project will be over the top. Sure hopes he gets it done soon, it'll look good sitting in my garage.
------------------ Ron
IP: Logged
08:17 AM
PFF
System Bot
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
My wife and friends would agree than I am certifiable on multiple fronts and prefer to take the hard way most of the time. I build my swaps to suit me and no one else. My old (and quite mild) SBC swap power band/dyno was very similar to most modified LS4 dyno's (through an auto) with my swap having slightly more wtq and whp due to a manual vs. auto... But while the performance was essentially the same, the LS4 is lighter, newer, more fuel efficient and has more potential... especially when coupled to a manual transmission. So if I am going to spend a year+ R&Ding a truly unique swap, I might as well give it an RPM band similar to a DOHC engine at the same time.
This was just my observation, not a "bash". Trying an overkill cam in a V8 is something every enthusiast should experience at least once. I've done it. I don't know if guru has, and either way, the flow and the electronics of the LSx allow much wilder cams to be daily-driveable. But even in the LSx world, some guys are backing down on the cam size per cube, as they've found out just how far is too far. Some build 6.7+ -liter strokers to keep their large cams, others swap to more modest specs. In guru's case, he can take it to 383 cubes if necessary, so that cam may prove good. Getting a 6.0L LS2 to pull 7200 RPM is no challenge, the recipe is already documented. I'm halfway on that path myself. But the beauty of the LSx is how it can make unbelievable HP at reasonable RPM levels. There is such a thing as too much power. Keep that in mind as you read this: Whatever the RWHP number for FieroX's amazing Fiero, my 6.0L combo will put down a bigger number. Not that I want bragging rights, or have a tiny thingie, or any of the usual reasons. I've set out to establish that a properly built Fiero can equal the performance tests results numbers of a stock Enzo. I really don't need this kind of power to be satisfied. But the LSx has more ultimate potential than a same-cost SBC, and more ultimate potential than whatever 3800 FieroX has been using to run low 10s. The V8 still has it's applications. I realize that a 1200 HP Ecotec has been done ( huge boost and race gas ) In fact, I think they're up to 1500 now. And that's far more than I need to beat the Enzo. But The LSX is good to 2500. More displacement IS more potential. Plus it's cheaper and easier to get 1500 from an LSx than a race-only Ecotec. The V8 isn't obsolete yet. But by the same token, I also have an L67 and a second cradle to bolt it to.
IP: Logged
08:46 AM
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
Mild, yeah right. That SBC was long on power and very cool in the way Paul put it together. A very impressive ride. His latest project will be over the top. Sure hopes he gets it done soon, it'll look good sitting in my garage.
The ZZ4 cam he was using IS mild. Not even 300 rwhp. I've seen the chassis dyno graph he posted. I saved a copy in my other PC. That 350 with that gearing really could have used a bit more cam.
IP: Logged
08:50 AM
Dennis LaGrua Member
Posts: 15734 From: Hillsborough, NJ U.S.A. Registered: May 2000
It all comes down to what you like. In the case of my 3800SC choice, it was made as it presented the best compromise between ease of installation, horsepower, torque, mileage, reliabilty and cost. With the current availabilty of aluminum V8s like the new LS3's one can now buy a light powerful engine to swap but it is costly to do and they do use more gas. On the other hand if you want a quick relatively easy swap at a moderate cost, some newer V6 designs offer some interesting possibilities. I enjoy the power of my 3800SC swap and appreciate the rock solid reliability and 27-28 MPG economy. I do not see the V8 swap going away but as gasoline gets more costly it may be a concern that drives the decision on engine choice.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
IP: Logged
10:01 AM
dratts Member
Posts: 8373 From: Coeur d' alene Idaho USA Registered: Apr 2001
I keep hearing about fuel economy of 3800s being better than lsx v8s. You are getting 28 mpg? I know that dog creek gets 30 mpg with his ls4 and he doesn't baby it. He has fun with it. I'll post my mpg, hp and 1/4 mile time when my turbo ls4 is finished. Car tuning (the supplier of my turbo kit) says to expect a gain of 2-3 mpg with the turbo set up. They're all good. We have amazing cars.
[This message has been edited by dratts (edited 05-18-2011).]
IP: Logged
11:17 AM
dratts Member
Posts: 8373 From: Coeur d' alene Idaho USA Registered: Apr 2001
I keep hearing about fuel economy of 3800s being better than lsx v8s. You are getting 28 mpg? I know that dog creek gets 30 mpg with his ls4 and he doesn't baby it. He has fun with it. I'll post my mpg, hp and 1/4 mile time when my turbo ls4 is finished. Car tuning (the supplier of my turbo kit) says to expect a gain of 2-3 mpg with the turbo set up.
IP: Logged
11:19 AM
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
I can't see a turbo helping the MPG of an LS4, stick or auto. I've read about other L67s going as high as 36 MPG, and I've yet to hear of an LS4 doing as well.
I can't see a turbo helping the MPG of an LS4, stick or auto. I've read about other L67s going as high as 36 MPG, and I've yet to hear of an LS4 doing as well.
Forgive my ignorance, but wasn't the turbo invented to help mileage? I really think it depends on how the engine is tuned to use the extra boost of a turbocharger.
quote
Originally posted by Trinten: Another reason I keep quiet is because... well, I'm an amateur. I openly admit that beyond the basics (changing the oil, spark plugs/wires and filling the cooling system, change brake pads/rotors), I'm a dummy when it comes to Fiero stuff, and I'm usually too worried that I'm going to seriously break something major to experiment/learn on my own without help/observation. I am one of those guys that would gladly pay someone to get things done, and I'll be happy to assist/be a tool gopher, and I always do my best to give credit where it's due.
That's exactly how I feel (though I don't have a swap). When it comes time for a swap though, I'll definitely want to help/watch the build, but I want to pay someone to do it right.
Originally posted by 1988holleyformula: Forgive my ignorance, but wasn't the turbo invented to help mileage? I really think it depends on how the engine is tuned to use the extra boost of a turbocharger.
Pretty sure that fuel mileage wasn't a huge concern in the early 1900s. First major uses were to compensate for power losses at lower air pressures (like at altitude in aircraft).
You could use a turbo to help with fuel efficiency as well, but to get a significant increase in fuel economy, you are not making any extra hp with it, and probably a bit less. Anyone claiming MPG gains from a turbo tuned to make a lot more power, is either talking BS, or the gain is so small as to be insignificant.
IP: Logged
03:39 PM
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
Turbos don't always help even diesels. It depends on the exact combination and circumstances. Superchargers, both belt driven and exhaust-turbine driven, were developed for fighter planes, first and foremost. Turbocharging a tiny engine, then running that in place of a same-HP, non-boosted engine can sometimes improve MPG. Or boosting a large engine may allow changing the gearing for more MPG when not using boost. But unless you go put the 2.86:1 FDR and the 33 / 37 sprockets in a 4T65E-HD, the LS4 cannot take advantage of this. Either that or a huge cam, which isn't turbo-friendly, so forget that. Even the F40-MT2 gearing isn't tall enough. Lower cruise RPM won't always improve MPG either, you can go too low. Again, it depends on the exact combination and circumstances. Edit: I was typing while Dobey was posting. That the gist of our answers agree is fortunate coincidence, and adds credibility.
[This message has been edited by Isolde (edited 05-18-2011).]
IP: Logged
03:42 PM
cooguyfish Member
Posts: 2658 From: Hamilton, OH, USA Registered: Mar 2002
personally, I had a saturn I turbo'd myself. I saw a mild fuel mileage improvement after the turbo (2-4 MPG) Sure I was running 94 octane which may or may not have made a difference. But I drove that car like I put the turbo on for fun (which I did), probably picked up 30-40 HP but still had better fuel mileage.
I believe the main idea behind turbo's doing better on fuel is really the fact you can downsize the engine so that when not making boost you have a little econo engine. But when you need the power the turbo steps it up for you. In my eyes similar to the DOD systems on the newer LS V8's.
Turbo's in and off themselves should help efficiency a bit even when just putting one an otherwise stock engine. Reason being that they are raising the compression ratio of the engine. Compression does give you more power but also better fuel mileage.
I'd speculate on this more but I only have the one personal experience on turbo's
IP: Logged
04:01 PM
PFF
System Bot
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
personally, I had a saturn I turbo'd myself. I saw a mild fuel mileage improvement after the turbo (2-4 MPG) Sure I was running 94 octane which may or may not have made a difference. But I drove that car like I put the turbo on for fun (which I did), probably picked up 30-40 HP but still had better fuel mileage.
I believe the main idea behind turbo's doing better on fuel is really the fact you can downsize the engine so that when not making boost you have a little econo engine. But when you need the power the turbo steps it up for you. In my eyes similar to the DOD systems on the newer LS V8's.
Turbo's in and off themselves should help efficiency a bit even when just putting one an otherwise stock engine. Reason being that they are raising the compression ratio of the engine. Compression does give you more power but also better fuel mileage.
I'd speculate on this more but I only have the one personal experience on turbo's
Oh hell, you missed it entirely. At low throttle openings, which you are using when trying to get MPG, there is no boost. When there is boost, there's fuel enrichment. In fact, you get enrichment before boost. But a 500 HP turbo engine needs and uses more fuel than a 500 HP N/A engine. Your results are suspicious. I can't disprove them, but you can't prove them with scientific precision, either.
Ok, since the question has turned into an argument, let me ask this: has anyone ever put a Pontiac V8 in a Fiero? The original engines where Chevy and Pontiac and we are talking about Chevy v Buick. So, why are there no Pontiac V8 swaps into a Pontiac? I know the answer to this is cost and availability, but what about the first question?
Originally posted by cooguyfish: Turbo's in and off themselves should help efficiency a bit even when just putting one an otherwise stock engine. Reason being that they are raising the compression ratio of the engine. Compression does give you more power but also better fuel mileage.
I'd speculate on this more but I only have the one personal experience on turbo's
You should not speculate. They don't increase compression ratio. They increase effective displacement. The air is compressed to a point before entering the cylinder, so it is a higher density of air, which is similar to having more air volume. The compression ratio in the cylinder itself doesn't change. Instead of compressing a cylinder full of 1 bar of air and however much fuel, it's compressing 1.1 or 1.2 (or however much the air is compressed) bar of air plus the fuel. Running very low boost with stock injectors will give you a couple MPG increase, because you're very slightly leaning out the mixture, and the IAT is increased a little, causing a slightly better atomization of the fuel. But getting 2-4 MPG is easy by other simple changes without a turbo.
The reason big turbos still see a 1-3 MPG increase at cruise speed, is because they're not making boost and power at 1500-1800 RPM, but the turbo is still warming the air and giving it a tiny little push.
Ok, since the question has turned into an argument, let me ask this: has anyone ever put a Pontiac V8 in a Fiero? The original engines where Chevy and Pontiac and we are talking about Chevy v Buick. So, why are there no Pontiac V8 swaps into a Pontiac? I know the answer to this is cost and availability, but what about the first question?
I keep hearing about fuel economy of 3800s being better than lsx v8s. You are getting 28 mpg? I know that dog creek gets 30 mpg with his ls4 and he doesn't baby it. He has fun with it. I'll post my mpg, hp and 1/4 mile time when my turbo ls4 is finished. Car tuning (the supplier of my turbo kit) says to expect a gain of 2-3 mpg with the turbo set up.
Not sure about mine, I have a LS376 and 5 speed (3.94) and I think i'm getting in the high teens on mileage. Have not figured it out yet, but at 70mph on the highway, im turning around 2800 rpm. I go through a tank of 93 octane pretty fast.
Ok, since the question has turned into an argument, let me ask this: has anyone ever put a Pontiac V8 in a Fiero? The original engines where Chevy and Pontiac and we are talking about Chevy v Buick. So, why are there no Pontiac V8 swaps into a Pontiac? I know the answer to this is cost and availability, but what about the first question?
pontiac grand prix has an ls4. Mine is an ls4 pontiac V8in a stretched fiero rebody.
IP: Logged
07:12 PM
cooguyfish Member
Posts: 2658 From: Hamilton, OH, USA Registered: Mar 2002
Oh hell, you missed it entirely. At low throttle openings, which you are using when trying to get MPG, there is no boost. When there is boost, there's fuel enrichment. In fact, you get enrichment before boost. But a 500 HP turbo engine needs and uses more fuel than a 500 HP N/A engine. Your results are suspicious. I can't disprove them, but you can't prove them with scientific precision, either.
Just so we are clear, when I said I only have experience with 1 turbo car that was N/A first, I don't mean I only have experience with 1 turbo anything.
I used to drive a turbo diesel commercial truck. If you looked at the throttle it made boost. Same with turbo diesel pick up trucks I've driven.
My TDI was hard to hear it but I'm pretty sure it made boost as soon as you started giving it throttle.
one thing I would say, I don't know if automakers put F/I on engines to increase efficiency or just power but I think we can all agree they don't spend the extra coin just for the fun of it.
quote
Originally posted by dobey: You should not speculate. They don't increase compression ratio. They increase effective displacement. The air is compressed to a point before entering the cylinder, so it is a higher density of air, which is similar to having more air volume. The compression ratio in the cylinder itself doesn't change. Instead of compressing a cylinder full of 1 bar of air and however much fuel, it's compressing 1.1 or 1.2 (or however much the air is compressed) bar of air plus the fuel. Running very low boost with stock injectors will give you a couple MPG increase, because you're very slightly leaning out the mixture, and the IAT is increased a little, causing a slightly better atomization of the fuel. But getting 2-4 MPG is easy by other simple changes without a turbo.
The reason big turbos still see a 1-3 MPG increase at cruise speed, is because they're not making boost and power at 1500-1800 RPM, but the turbo is still warming the air and giving it a tiny little push.
The only reason I mentioned them raising compression is because I read somewhere that I can't find now that you could raise compression physically with pistons, or mechanically with turbos (or something to that effect).
No, I really don't know enough about this to argue, but that's where I'm coming from.
More on it later
IP: Logged
07:17 PM
dratts Member
Posts: 8373 From: Coeur d' alene Idaho USA Registered: Apr 2001
Pretty sure that fuel mileage wasn't a huge concern in the early 1900s. First major uses were to compensate for power losses at lower air pressures (like at altitude in aircraft).
You could use a turbo to help with fuel efficiency as well, but to get a significant increase in fuel economy, you are not making any extra hp with it, and probably a bit less. Anyone claiming MPG gains from a turbo tuned to make a lot more power, is either talking BS, or the gain is so small as to be insignificant.
I won't have a previous install to compare to since I'm doing the turbo at the same time as the swap, but Kevin at cartuning has over 200 turbo kits out and running with no problems and 505 whp dynoed which comes out to about 640 hp. His customers have reported 2-3 mpg gains. Maybe BS but there are a lot of people reporting these results. I'm still amazed that you can boost a hgh compression engine like these. I think that a big part of it is the LS heads, intercooler, and meth injection. I'm sorta talking out my ass since my swap is still not finished, but it's close. I'm not trying to bash anyone or start a flame war. Just passing on the information I have.
IP: Logged
07:24 PM
dratts Member
Posts: 8373 From: Coeur d' alene Idaho USA Registered: Apr 2001
You should not speculate. They don't increase compression ratio. They increase effective displacement. The air is compressed to a point before entering the cylinder, so it is a higher density of air, which is similar to having more air volume. The compression ratio in the cylinder itself doesn't change. Instead of compressing a cylinder full of 1 bar of air and however much fuel, it's compressing 1.1 or 1.2 (or however much the air is compressed) bar of air plus the fuel. Running very low boost with stock injectors will give you a couple MPG increase, because you're very slightly leaning out the mixture, and the IAT is increased a little, causing a slightly better atomization of the fuel. But getting 2-4 MPG is easy by other simple changes without a turbo.
The reason big turbos still see a 1-3 MPG increase at cruise speed, is because they're not making boost and power at 1500-1800 RPM, but the turbo is still warming the air and giving it a tiny little push.
I think we're talking semantics here. Air is compressed and then compressed again in the cylinder. I think they add up to an effective higher compression ratio. I don't see where warming the air in a turbo is helping (giving it a tiny little push) I'm taking some of the turbo heat out with an air to water intercooler.
Wow... three pages on this... All I can say is I went V8 LS4 because I did research, got advice from an experienced swapper and just liked the thought of it. Like most/many of the 3800 guys, and LS4 guys and SBC guys, I Love my car and if I had it to do over again, I would do exactly the same thing..
So, to answer the original post... shucks, not sure why there are fewer SBC threads these days... Maybe just cause there is a lot more to choose from now "engine wise" and lots of new stuff to try swapping...
Originally posted by dratts: I think we're talking semantics here. Air is compressed and then compressed again in the cylinder. I think they add up to an effective higher compression ratio. I don't see where warming the air in a turbo is helping (giving it a tiny little push) I'm taking some of the turbo heat out with an air to water intercooler.
I don't think it's semantics. The volume at BDC vs volume at TDC are what determines the CR. The compression of air from the turbo does not alter either one of those; having compressed air enter into the cylinder from the intake only means that there are more air molecules in it than there would otherwise normally be. If your CR is 10:1 N/A, it is still 10:1 on 20 psi of boost if the heads were never pulled to change it during the turbo install. Let me give a better example to explain how it means effectively higher displacement:
Suppose you have a 2.5L 4 cylinder. And let's say it has a CR of 10:1, and makes 150hp NA. What RPM it makes it at is irrelevant. It's not bad, but you'd like some more power. So you get a turbo, intercooler, injectors, and everything necessary for a turbo install. You get everything installed and tune the turbo to make 14.7 psi of boost. Now you're making about 300hp.
Now, 14.7 psi is 1 atmosphere. In NA form, you were already displacing 2.5L of air and fuel molecules, at 1 atmosphere. Since the turbo is compressing at 1 atmosphere before entering the engine, what you've just done is effectively doubled your displacement by fitting 2 atmosphere of air into 2.5L of volume, giving you an effective displacement of 5.0L. All things being equal in materials, strength, airflow, and other general design of the engine, a 5.0L V8 with 10:1 CR and that 2.5L at 14.7 psi of boost, will make about the same hp, with different peak torque, and different power curves.
Now, as for the comment about the turbo helping at cruising speeds "with a little push" and "warming the air slightly," I was talking about the slight increases in MPG that people see with turbos. At cruise RPM, even though the turbo isn't producing any "useful" boost for making power, the blades still spin and force a tiny bit more air into the intake, with a slight turbulence, and the air is heated as well, even if only very slightly. Both of these things help the fuel atomize better. So a very tiny (1-2 MPG) increase in fuel economy is expected, but not an amazing feat. Most people would gain that if they just paid attention to their tire pressure and take their foot out of the gas. Going 90 isn't going to save you any money, especially when you end up on the side of the road with a reckless driving ticket. I hear insurance companies frown upon those pretty badly.
Originally posted by dratts: I won't have a previous install to compare to since I'm doing the turbo at the same time as the swap, but Kevin at cartuning has over 200 turbo kits out and running with no problems and 505 whp dynoed which comes out to about 640 hp. His customers have reported 2-3 mpg gains. Maybe BS but there are a lot of people reporting these results. I'm still amazed that you can boost a hgh compression engine like these. I think that a big part of it is the LS heads, intercooler, and meth injection. I'm sorta talking out my ass since my swap is still not finished, but it's close. I'm not trying to bash anyone or start a flame war. Just passing on the information I have.
Yep. I wasn't trying to say the 2-3 MPG claims were not feasible or were just BS. They are however, insignificant, and any number of changes without a turbo could result in that much gain in MPG. It's the ones that try to claim they installed twin turbos on a vette and are making 750hp now on a stock LS3, and getting 15-20MPG more than the EPA rated value. Those are total BS, and would very little, if anything, to do with installing turbos. The 750 hp makes sense. The 42 MPG highway at 70 MPH in an automatic LS3 Vette, though, are total BS.
Is your swap running yet? Any video of it making even a little boost to tease everyone with?
IP: Logged
09:14 PM
dratts Member
Posts: 8373 From: Coeur d' alene Idaho USA Registered: Apr 2001
Joe got it to fire. We're waiting for Kevin to get a good tune downloaded to us. For the few seconds that it fired with no tune it sounded pretty mean.
IP: Logged
10:37 PM
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
it depends on the turbine side of the turbo. turbos with a large turbine dont restrict exhaust flow much, but they take longer to spool up. smaller turbine, quicker spool- but more exhaust restriction
this combined with the tune needed after the turbo install will also determine MPG. theres even more factors than that, but those are a few of the bigger ones
I've never got better MPG with a turbo install. either the same, or maybe just 1-2MPG less
Is this on the road?? I've been waiting for an LS4 manual solution and this sounds ideal.
As of my last visit with Paul, he was getting closer to getting this done. Check out his thread in the "Construction Zone". Paul does some amazing work.
realy though does it matter as long as it goes fast and does what the owner wants, nope. In the end its a fiero and its the car that brought us all together. 3.4 3400, 3800, sbc, lsx and all swaps inbetween. Share in the fieroness and stop the swap hate.
Maybe just cause there is a lot more to choose from now "engine wise" and lots of new stuff to try swapping...
