I am getting a 94 Camaro next week and will be pulling the engine out. I have read that people stated the engine doesn't have much breath after 4500RPM. People have claimed that the engine just doesn't get the air supplies it needs. I am going to install 1.52 rockers with a 260 cam shaft.
Here is my dilemma:
You have a few options with the plenum that you can go with.
A dawg modified Fiero plenum:
Trueleo (not a fan of the look, but if it works good I might have to go with this):
A WCF plenum (This is what I want.)
OR, possibly the best option, a dual throttle body intake that was made by TLG (now known as BTR)
Which one is going to give me the best chance of getting more air into the engine? I have to assume some of you could give me some opinions or even facts that back up your opinion. I appreciate your help, and watch for a build thread soon
------------------ Every fiero has a story, It's our job to keep that story alive.
[This message has been edited by zzzhuh (edited 06-26-2015).]
The TLG dual body is a beautiful unit. You can ask Yellowstone on here since he has one on his car. However the last I remember, they made the car run VERY rich and the guys at TLG were working on a solution for that issue. To date, I haven't heard of a fix but I may just be out of the loop.
The one from Francis (Trueleo) is also very nice. It seems to be the favorite because of the larger air canister and intake tubes and makes quite a difference. The throttle response is almost instant.
From what I understand, the one from Dawg also works very well. He improved one of the true weak areas of that plenum and has the same fast throttle response.
I wouldn't waste my time with WCF so no comment on them.
My goal is to someday try adding a secondary (small) TB onto the passenger side of the stock upper plenum that would start to open only when the primary TB is around 3/4 open (and both would be completely open at full throttle). The secondary TB could be operated with direct linkages, or perhaps (and I like this idea better) with a vacuum control of some sort. IMO, this would bypass the problem with the restrictive stock intake neck and still retain crisp throttle response at lower RPMs.
Go ahead and run with my idea!
[This message has been edited by Patrick (edited 06-28-2015).]
My 3.4 pulled very well all the way to 6000 and I had a trueleo, 260 cam, 1.6 full roller rockers, and alot more. I swapped my 3.4 out for a 3800SC so I have my intake for sale if you are interested. Truleo stopped making these so if you wanted to go that route it will be a little harder to find
I went with the Dawg mod and a Daniel Morris bored throttle body. The result is instant and great. You might run too lean so watch carefully. In my case, I had to get a new tune, so beware of unforseen expenses.
My goal is to someday try adding a secondary (small) TB onto the passenger side of the stock upper plenum that would start to open only when the primary TB is around 3/4 open (and both would be completely open at full throttle). The secondary TB could be operated with direct linkages, or perhaps (and I like this idea better) with a vacuum control of some sort. IMO, this would bypass the problem with the restrictive stock intake "throat" and still retain crisp throttle response at lower RPMs.
Go ahead and run with my idea!
Here ya go, Patrick. Set up to only open at part throttle like the secondaries of a 4-barrel carb. He said it's a real kick in the rear when it opens.
I went with the Dawg mod and a Daniel Morris bored throttle body.
I think you mean Darrel Morse?
Side note: when I upgraded to a Trueleo intake with a bigger throttle body, I noticed the engine was going really lean for a brief moment, every time I hit the gas. I had to increase the acceleration enrichment significantly to adjust for it. A few other things had to be tweaked and tuned too.
The math says the stock one will flow enough for a 3.4. The biggest thing I found limiting rpm was the stock coil. When I went with really good plug wires and a better coil it pulled harder in the upper rpms, when I went to DIS, pulls till redline.
I wouldn't waste my time with WCF so no comment on them.
Why do you say this?
quote
Originally posted by Patrick:
My goal is to someday try adding a secondary (small) TB onto the passenger side of the stock upper plenum that would start to open only when the primary TB is around 3/4 open (and both would be completely open at full throttle). Go ahead and run with my idea!
That is a great idea Patrick! The dual throttle body actually had an adjusting screw for the second throttle body, so you probably could make it open the way you would want it to.
The reason they stopped making this: $2,000 for the intake.... Anyone make these for cheaper? I have seen threads with dual throttle bodies and they looked a little different.
Edit to add: Here is the link, scroll down and you will see it.
[This message has been edited by zzzhuh (edited 06-27-2015).]
Here ya go, Patrick. Set up to only open at part throttle like the secondaries of a 4-barrel carb. He said it's a real kick in the rear when it opens.
Yes, I've seen that one posted previously, and it certainly influenced me! What I don't like about that particular setup however is that you either run with no air filter, or you need to cut a hole in the decklid. That's why I'd like to have the secondary TB connected to the passenger side of the upper intake plenum (probably with a tube of some sort between the plenum and the TB). IMO, the secondary TB also wouldn't have to handle a whole lot of CFM, as it only needs to supplement the airflow that the stock neck of the intake plenum restricts at WOT.
[This message has been edited by Patrick (edited 06-28-2015).]
Patrick, that is a picture I took at the 2007 RFTH. It's Ken Wheeler's GT. I believe he said it was a motorcycle carb. Quite likely since he owns Wheeler Performance Cycles, just south of The Dragon. I suppose a decklid scoop of the Mustang style could be grafted onto the decklid, giving clearance for an air filter. Maybe have the injectors resized to 16 lb for a stock 2.8 so it didn't lean out at high rpm. I wonder how this would be accepted under SCCA rules.
I think the addition of a smaller secondary TB is definitely something worthwhile to try, especially if any other "breathing" areas of the engine have been improved.
[This message has been edited by Patrick (edited 06-30-2015).]
Ok, so here are some pictures that describe the issue that GM already knew about with the stock intake. Here is a picture of the stock intake. Note the areas that I circled:
Here is the intake on the PPG car that is owned by Fred. GM got smarter here. Notice the areas that are now filled in and opened up inside the plenum for more airflow:
Also notice how the intake is thicker. You can see the weld line:
This is what one of our members named Fierochild did to his. It is almost exact to what they did to the PPG car:
Also enlarged the restricing neck and removed all of the internal runner walls:
Here is the bottom:
And mounted on his car:
You can see he basically did what the Dawg intake improves on the neck end and then modified the plenum more to be like the PPG intake. Also if you notice in my picture of the PPG car's weld line on the bottom of the plenum, it looks to be in the exact location as the bottom picture of Fierochilds weld line.
By the way, here is the bottleneck of the system. This is the intake neck cut down with a 57mm gasket. Notice how much airflow is lost:
[This message has been edited by IMSA GT (edited 06-29-2015).]
--> Fierochild, how did your modified intake work? Did this use the stock throttle body?
--> zzzhuh, what option did you pick for your 3.4 swap?
I saw this at the top of the forums and went "That looks familiar"
I have yet to fully build my 3.4, but I have decided to go with the stock 2.8 plenum. I will however be using the DAWG mod, and customize it as IMSA suggested.
Originally posted by Notorio: ... --> Fierochild, how did your modified intake work? Did this use the stock throttle body?
Fierochild sold all of his Fieros, so I don't think he'll see this.
The intake worked quite well. He was using Darrell Morse's throttle body, unless I'm mistaken. His car dynoed 170-something at the wheels, through a Getrag. It was easily 200+ at the crank. This was on a 3.4. I think he had DOHC pistons in it, so it ran a little higher compression. He maybe could have gotten a few more HP out of it with a Trueleo, but he was running SCCA ITB (I believe) and wanted it to look as "stock" as possible.
Here is a write up with test results on my intake and Bored Out TB. I wanted to keep the look of the Fiero engine but get better performance than the GM engineers took the time to design. The restricted area of the plenum was reworked with retention of the EGR hook-up . . https://www.fiero.nl/forum/Forum2/HTML/118417.html . Not many have actually had airflow testing completed and Brucepts was up to the challenge. ------------------ Mark ' 85 2m6 3.4PR In the Great Northwest!
[This message has been edited by NW-Fiero (edited 08-28-2015).]
I am getting a 94 Camaro next week and will be pulling the engine out. I have read that people stated the engine doesn't have much breath after 4500RPM. People have claimed that the engine just doesn't get the air supplies it needs. I am going to install 1.52 rockers with a 260 cam shaft.
Very true because compressed air will increase air supply dramatically but not everyone is eager to bolt on a turbo. I still feel that its the best solution for overcoming intake restrictions but it can be costly and requires a 2 BAR MAP and a re-engineered ECM program with new fuel tables. The most economical solution may be to use the Camaro/Firebird 3.4L P/R Plenum and run DIS with the 7730 ECM. Re-wiring the original harness is not very difficult and loads of programming support is available.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, 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 "
I have 2 fiero 2.8 intake plenums for sale (one engraved) and a middle plenum and LIM if anyone wants to buy them to mod.
PM me if interested
------------------ ===Always trying to find time to work on cars=== Louis Duet Baldwin, Long Island, NY "My mind spins like helicopter blades." -G. Rossdale ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ "Blue" <= '85 Fiero GT 3800sc series 2 ~~~~~~~~~~~~~~~~~~~~~ "Boo" <= '81 Delorean DMC-12 VIN #5835 Stock PRV engine Peugot 604 Intake manifold Exhaust headers Anti-3rd brake light
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