quote Originally posted by JazzMan: The .800 is referring to the voltage put out by the O2 sensor in the exhaust stream, it is 800 mV, or .800 volts DC. Now here's where it gets complicated. The normal O2 sensor puts out a voltage that's relative to the oxygen content in the exhaust, it is not proportional to the amount of O2. Because of the very narrow range where it is sort of proportional, which is right around the stochiometric air/fuel ratio of 14.7/14.8:1, the factory O2 sensor is used more as a lean/rich indicator switch rather than as a measure of the actual amount of O2 in the exhaust. Once you get much out of this range the sensor is unuseable, that's why the ECM goes to preprogrammed tables at WOT because the engine needs to be run slightly rich at WOT and the O2 sensor doesn't work at that richness. In effect, at WOT the ECM is in open loop and cannot adjust the mixture based on changes in exhaust O2. The dyno people need to know what the O2 content is outside of the useable range of the factory O2 sensor, so they use what's called a Wideband sensor. It is capable of measuring exhaust O2 amounts that correspond with mixture ratios of around 10:1 to as high as 18:1, sometimes higher. BTW, the V-tec uses a wideband sensor, one of the reasons it is a little more efficient, but at $200/pop those sensors are too expensive for most applications. The A/F ratio on the dyno sheets is calculated using the wideband (WB) O2 sensor readings and shown on the dyno display. JazzMan

Jazzman,

Out of curiosiity, in norma; operation does the O2 sensor have a direct effect on the fuel or is the ECM just looking at it and coming up with a bias to add to a fuel value it gets from a table?

The O2 sensor doesn't "control" the fuel delivery per se. Roughly, the ECM looks at the RPM MAP, CTS, IAT, and TPS readings, and looks at a table for fuel and timing. It looks at the O2 sensor readings that result, and if different than what it expects it modifies the fuel delivery and stores a short term adjustment. If the adjustment is needed often enough it stores the adjustment in long term. That adjustment is applied to the mixture and is part of how the ECM adapts to changing engine conditions over time. The amount of adjustment is limited, so big engine changes require reprogramming the PROM.

I only have a basic understanding of the details, but there are lots of excellent websites out there that go into the subject in more detail.

JazzMan

quote Originally posted by stevegibbs: I wouldnt' screw with chips anymore. Get an aftermarket fuel computer, hit a dyno, spend 2 hours on it max, and have the A/F ratio at 12.5:1 across the board when you go WOT. Chips take forever to replace and dyno and just keep having to go back to the dyno many times. I dont' see why you keep wanting to do preprogrammed chips.

Do you have any that I can test for you?

So which aftermarket fuel computer are you using?

It's not that hard for the people that know how to burn the chips and have the equipment to tweak them, and Westers will keep tweaking for you for a long time once you've bought the first chip from them.

The Megasquirt is a viable option if you're an electronics hobbiest and want to tinker with it a lot, but it wouldn't go into my daily driver. The GM computers are really quite versatile and reliable and the chips take but a few seconds to change (but longer to program and burn).

John Stricker

quote Originally posted by stevegibbs: I wouldnt' screw with chips anymore. Get an aftermarket fuel computer, hit a dyno, spend 2 hours on it max, and have the A/F ratio at 12.5:1 across the board when you go WOT. Chips take forever to replace and dyno and just keep having to go back to the dyno many times. I dont' see why you keep wanting to do preprogrammed chips.

GREAT DOCUMENTATION AND PRESENTATION !!! You definitely deserve a + for all your effort. I found it to be great! Also, I really respect people that experiment with their cars. Thanks.

Phil

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87 FIERO GT 2.8 5spd

GM auto tech for 27 years. Specializing in electrical and computer problems. Now on workers comp. and it looks like I will be unable to return to work as a tech.

I understand what you're saying John, but an aftermaret programable computer or even a good piggeyback is what he needs here.

Even if Westers will teak indefinitely, how many trips to the dyno do you really want to make between burns?

I've worked with Electromotive, Haltech and the Power Commander if you're interested.

quote Originally posted by jstricker: So which aftermarket fuel computer are you using? It's not that hard for the people that know how to burn the chips and have the equipment to tweak them, and Westers will keep tweaking for you for a long time once you've bought the first chip from them. The Megasquirt is a viable option if you're an electronics hobbiest and want to tinker with it a lot, but it wouldn't go into my daily driver. The GM computers are really quite versatile and reliable and the chips take but a few seconds to change (but longer to program and burn). John Stricker

Howard,

I understand completely. My Scout has the Holley ProJection and the Northstar will have CHRFab's Commander 950. But now we're talking a whole new entry into $$$. That's up to Alex how far he wants to take it now. As I said before, this has been educational. I think Alex is pretty close with his thoughts that 160 rwhp is all the Fiero mid and lower manifold are going to support. The gains he's going to get with cam, chips, and rockers will be minor, but he doesn't need a whole lot to get where he wants to go either, so I think he just might make it.

Again, if I were staying with a 3.4 or 2.8, I'd most likely get an aftermarket 4 bbl manifold and use the ProJection if I wanted to stay pretty cheap or the Commander digital if I wasn't afraid to spend more money. Going that route, I think 180 or so rwhp is obtainable.

John Stricker

quote Originally posted by Howard_Sacks: I understand what you're saying John, but an aftermaret programable computer or even a good piggeyback is what he needs here. Even if Westers will teak indefinitely, how many trips to the dyno do you really want to make between burns? I've worked with Electromotive, Haltech and the Power Commander if you're interested.

quote Originally posted by jstricker: So which aftermarket fuel computer are you using?

I am going with an Apex-i SAFC2 for my car. It alters the map signal to the computer so that it will dump more or less fuel based on the map and TPS signal It will work pretty much with any car that has a Map sensor. HKS also makes an add on fuel controller as well that can be adapted to work on the fiero. These units allow multiple rpm adjustment points to adjust fuel. If you are lean down low then richen it up. If you are rich up top then lean it out.

Howard is on the same page as me. How many trips are you going to have to make to the dyno in order to get the perfect chip where your a/f ratios are perfect throughout the rpm range? Think of it this way. Most dynos charge like 65 dollars for 2 pulls abouts or for each time you go. If you go three times thats about $195 for dyno tuning alone. and thats only going 3 times. How many trips do you think it will take to get it exact with chips? I will say well more then 3. Alex has 2 that I know of and looking at his a/f ratios he has many more trips ahead of him. If you bought a fuel computer you make one trip, pay for the one or two hours to have it tuned, and you are done. Thats it! An Safc on ebay can usually be found for $200 or less. So $200 plus 2 hours of dyno time comes out to $200 for about $400 total dollars to get the car tuned right.

Westers charges how much for the first chip? So factor that into the cost and then all the subsequential dyno trips to get the ratio correct. You can see where an aftermarket computer comes in handy now.

plus who wants to make 15 dyno trips and take time out of their day to schedule and then have to keep going back and back and back. Personally I would just want to go once and be done with it. Thats what this SAFC will do for me.

Steve

I would seriously consider the AEM EMS over the Holley unit. It's about the same price and I feel you get a lot more.

quote Originally posted by jstricker: the Northstar will have CHRFab's Commander 950.

John and Alex, Excellent work!
As for your dyno readings and future changes, By my calculations (mind you this is just an estimate going by what you posted) That intake should flow somewhere around 350-360cfm. This is about perfect for a 3.4L.
Per the dyno readings, you are now getting close to the flow limit of the stock cast heads. I think you would have seen better gains with ported heads and a better cam. Right now Alex is running the stock cam. This is smaller than the cam in a stock Fiero engine. If Alex plans on just doing a cam swap, I wouldn't put in the H272, I would go with the H260. The heads are going to be a restriction point now. If you want to use the H272, Then I would suggest getting the heads ported.

The problem with using the 2.8-3.4 cast headed engines is first the intake, It would appear you guys have succeeded in getting past that or at least matching the intake to the displacement of the engine. Per Alex's mod list he's using headers and a Borla.
Now you just need to equalize the actual flow thru the engine. This is where the cams and head flow now comes in.

Cams vs Head flow: No matter how many different cams I use in Desktop Dyno, The H260 cam appears to be the perfect size cam with the stock head flow data. This is based on gains vs. lift. Anything larger than .455 lift and you gain less power per .005 lift. Depending on your head porting, A mild port job will move your power lift to about .475 and a max port with SS valves peaks about .490. If you want to match a cam to a known head flow, What I did was use a 3.4L engine. For intake I used a 700cfm TPI, and for exhaust I used "large headers no muffler". (this basically gave me an unrestricted intake and exhaust so I could have a baseline of max flow so the head/cam data could be compared equally.) Then plug-in the head flow data. (I have stock, mild port, and full port with SS valves) I used the Camdisk 2 and plugged in every cam they had listed for a 60* V-6.

I think you guys should now start contacting Holley or Edelbrock or ???? and see about making an aftermarket version. With all the 3.4L swaps that have been done, and the many more to come, This would be a very useful if not almost required part.
Again, Excellent work, I look forward to seeing how much more gains Alex gets once he gets into the heads and cam.

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Happiness isn't around the corner...
Happiness IS the corner.

I've got no problems with anyone that wants to use a piggy-back type unit or switch to an ECM that's really made for a different car and then spend the time adapting and wiring. When it's done, and working properly, I'll buy you all a beer and help celebrate the fine work.

In the case of the Northstar, the only unit out there that is sold as plug and play for the engine is the CHRFab units. The 950 is boost capable with the proper MAP sensor and laptop configurable. The electormotive units are good, but require an external trigger wheel that I don't like. There are a lot of options out there if somebody wants to spend a lot of time adapting, wiring, and fabricating.

The AEM unit is not made for the Northstar trigger wheel and dual crank sensors. It's not made for the GM sensors. It may be a fine unit, but I don't want to have to spend a couple hundred hours getting it wired up and then develop my own initial settings on the software. With the Holley from Allan, I don't have to. It's modified to be plug compatible and comes with a baseline program that he's had success with and knows is in the ballpark.

As far as not making additional trips to the dyno as Steve mentioned, that's certainly valid if, and only if, you have your engine with the components like cam, rockers, compression, intake, TB, etc., all decided on, in place, and then LEAVE IT ALONE. I actually think that Westers can get pretty close with a chip if Alex sends them the dyno graphs and charts that show torque, hp, rpm, and A/F. If he had a way to graph the MAP, that would be useful to them as well. If you make any changes to your combination then regardless if you have a chip or a laptop, it's going to be back to the dyno to optimize things again.

Although I don't share your enthusiasm for spending that much more money on a programmable computer, you comments are certainly valid and worth considering for people that are looking at that aspect of it.

John Stricker

Looking more closely now at that A/F chart I do really need to richen up that puppy. But I need to ground this car for a clutch/cam job so ti will have to wait

quote Originally posted by jstricker: As the rpm's come up and the torque and hp rise, the A/F is getting richer, which is normal. Almost every chart I've EVER seen looks something like Alex's first two, a richening mixture, dramatically so once you pass peak torque. On other charts, it may flatten out some, but I've never seen the "hump" that is in this chart (the circled area) before. I wasn't surprised to see that the curve was much steeper and started much leaner, more air coming in. I've been trying to think of a reason WHY that hump occured there, and haven't come up with one yet.

It looks like you might have a flow problem at the mid RPM range. This could be caused by turbulance. The Intake can flow about 350-360cfm. But the throttle body is only 325cfm (The bored TB is 57mm, stock is 52mm) My guess would be as the engine hits 3500 rpm, the TB cannot allow enough air in to compensate for the increased plenum volume. Think of it this way, As the engine is drawing air in, the TB cannot replace the plenum volume as quickly. This would cause some low pressure turbulance. As the rpm keeps increasing, the velocity of the flow decreases turbulance. If the pressure changes rapidly from the turbulance the MAP sensor may have a problem reading the rapid changes or the ECM may be trying to to adjust, but the difference/speed in readings may be too much for it to adjust correctly/accurately.

The way to confirm this would be to get a reader and hook it up to the ECM. Monitor the MAP sensor readings and if at 3500rpm or so they start to change rapidly, Then turbulance is the problem. On the dyno graph, at about 5000 rpm it seems to smooth back out. This is probably because the velocity of the flow is over-taking the turbulance.

As for possible fixes, You could try going to a larger throttle body. See if you have enough to open the snout another 3mm. I don't know if it's possible, But the bored TB is 57mm, To reach 360cfm, You would need a 60mm TB. Since Darrell Morse is the most knowledgable on boring the TB's, You could ask him if it is possible to to go that large.
Since the turbulance appears in the 3500-4500 rpm range, a fin down the center of the plenum might help. Sort of the same principle of the fin in the heads.

[This message has been edited by Oreif (edited 03-01-2004).]

The Electromotive units are garbage and I was just recommending you check out what the AEM can do before dropping $1k on the 950. I don't know N* specifics.

I do appreciate plug and play and the convenience of getting a basemap from CHRFAB. Starting with all zeros sucks.

One thing about making trips to the dyno after mods is that with the AEM, you can tell it what A/F you want it to run and with the aid of a wideband, it can self-learn and tune itself. It also has datalogging and traction control built-in.

quote Originally posted by jstricker: In the case of the Northstar, the only unit out there that is sold as plug and play for the engine is the CHRFab units. The 950 is boost capable with the proper MAP sensor and laptop configurable. The electormotive units are good, but require an external trigger wheel that I don't like. There are a lot of options out there if somebody wants to spend a lot of time adapting, wiring, and fabricating. The AEM unit is not made for the Northstar trigger wheel and dual crank sensors. It's not made for the GM sensors. It may be a fine unit, but I don't want to have to spend a couple hundred hours getting it wired up and then develop my own initial settings on the software. With the Holley from Allan, I don't have to. It's modified to be plug compatible and comes with a baseline program that he's had success with and knows is in the ballpark. As far as not making additional trips to the dyno as Steve mentioned, that's certainly valid if, and only if, you have your engine with the components like cam, rockers, compression, intake, TB, etc., all decided on, in place, and then LEAVE IT ALONE. I actually think that Westers can get pretty close with a chip if Alex sends them the dyno graphs and charts that show torque, hp, rpm, and A/F. If he had a way to graph the MAP, that would be useful to them as well. If you make any changes to your combination then regardless if you have a chip or a laptop, it's going to be back to the dyno to optimize things again. Although I don't share your enthusiasm for spending that much more money on a programmable computer, you comments are certainly valid and worth considering for people that are looking at that aspect of it. John Stricker

Oreif,

Your thinking is kind of along the same lines as mine but I was leaning more towards a reversion effect out of the runners (or some of the runners) because of the much larger plenum volume. This upper, with it's larger plenum, is going to have air tht goes through the TB at moderate to high velocity and then slows down dramatically in the plenum. It will then have to accelerate a lot as it's pulled into the runners. Your idea of turbulence, maybe between the two runners on each side that butt against each other, is certainly possible, but individual runners do funny things at high rpm's so it's hard to tell. I've seen very fine mists of fuel standing about 2" abover a Crower injector tube with the engine at WOT and 7,000 rpm. Because we don't have data for individual cylinders we can't tell for sure if it's turbulence/reversion in the main snorkel area or if it's just an effect on some cylinders, like the ones closest to or furthest away from the air inlet.

I don't think the TB can take much more porting. To go any further we might as well use a different TB like the dual bore on the LT1 or the single bore on the later Northstar/Auroras that use the IAC valve (not the stepper motor). Of course the next problem we'd run into would be height. I already had to "squash" the tube slightly or I was going to have hood clearance problems and that would be even more noticable as we get larger. I've got an extra one that I could take the butterfly out and bore to destruction to find out how far it could be taken, though. Hmmmmm....bored to destruction.............I kind of like the sound of that!

John Stricker

quote Originally posted by Oreif: It looks like you might have a flow problem at the mid RPM range. This could be caused by turbulance. The Intake can flow about 350-360cfm. But the throttle body is only 325cfm (The bored TB is 57mm, stock is 52mm) My guess would be as the engine hits 3500 rpm, the TB cannot allow enough air in to compensate for the increased plenum volume. Think of it this way, As the engine is drawing air in, the TB cannot replace the plenum volume as quickly. This would cause some low pressure turbulance. As the rpm keeps increasing, the velocity of the flow decreases turbulance. If the pressure changes rapidly from the turbulance the MAP sensor may have a problem reading the rapid changes or the ECM may be trying to to adjust, but the difference/speed in readings may be too much for it to adjust correctly/accurately. The way to confirm this would be to get a reader and hook it up to the ECM. Monitor the MAP sensor readings and if at 3500rpm or so they start to change rapidly, Then turbulance is the problem. On the dyno graph, at about 5000 rpm it seems to smooth back out. This is probably because the velocity of the flow is over-taking the turbulance. As for possible fixes, You could try going to a larger throttle body. See if you have enough to open the snout another 3mm. I don't know if it's possible, But the bored TB is 57mm, To reach 360cfm, You would need a 60mm TB. Since Darrell Morse is the most knowledgable on boring the TB's, You could ask him if it is possible to to go that large. Since the turbulance appears in the 3500-4500 rpm range, a fin down the center of the plenum might help. Sort of the same principle of the fin in the heads.

Still be nice to see what if anything a bigger TB would do. But thanks anyway cause I feel a lot better about buying that new turbo yesterday. I was going to build a ground-up manifold to take advantage of all the mods I've done (it of cause ran out of air), then we decided on a turbo instead. We'll be burning our own chips till we get just what we want. I'll post all the details and dyno charts when we're done. We should have done in time for Carlise.

quote Originally posted by jstricker: I don't think the TB can take much more porting. To go any further we might as well use a different TB like the dual bore on the LT1 or the single bore on the later Northstar/Auroras that use the IAC valve (not the stepper motor). Of course the next problem we'd run into would be height. I already had to "squash" the tube slightly or I was going to have hood clearance problems and that would be even more noticable as we get larger. I've got an extra one that I could take the butterfly out and bore to destruction to find out how far it could be taken, though. Hmmmmm....bored to destruction.............I kind of like the sound of that!

What about this one? (You would need to convert the end of the snout to a J-body bolt pattern.)

RSM 2.8L/3.1L 62mm Throttle Body- $299.99
J01022F/J

RSM's 62mm throttle body gives you the air flow you need. Utilizing a factory throttle body and boring it out to 62mm, this item is a direct bolt-on.
This item is for the 2.8L and 3.1L engines only. It does not fit the 3100 engine.

www.highrevmotorsports.com/catalog/product_info.php?cPath=27_31&products_id=996

[This message has been edited by Oreif (edited 03-01-2004).]

Don't let this thread die!

any updates?

John, that's some beautiful re-engineering on that plenum. I wouldn't want to go that route though as I believe that there is only so much that can be gained from reworking this plenum.
Take a look at the area inside the lower passageways of the middle manifold where the injector sits. Not much room there -right? You can port this area some as I did on my 3.4L but ultimately for my application, the turbo proved the solution. While your new design seems to have done much for the upper plenum I would say that the middle manifold will now become the prime restriction. What do you think?

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87GT 3.4 Turbo Best 0-60 5.2 seconds
http://www.turbochargerpower.com/turbo.htm

I, too, was going to suggest the middle plenum. The air passageways going down to the lower plenum are tiny at the top, then open up to a large rectangle at the lower plenum. I know Oreif said that you're probably around maximum flow for the displacement right now, but I can't help but think that the middle plenum is still a problem. If nothing else it would give you more volume (if you opened it up or made a new one), which should make for a little more torque. Definately will allow for better flow.

I'm also interested in that 62mm Throttle Body Oreif showed. I'm not looking under the hood right at the moment, so I'm curious what kind of modification it would need to mount on the Fiero intake.

Just curious... why dont the HP and TQ figures cross at 5252 RPMS? Mathematically they must, HP = TQ * RPM / 5252 right?
BTW, I have an idea...
(forgive the feeble attempt on M$paint)
Before:

After:

quote Originally posted by Fierobsessed: Just curious... why dont the HP and TQ figures cross at 5252 RPMS? Mathematically they must, HP = TQ * RPM / 5252 right?

You're correct.

They don't cross at 5252 on this graph because they're on different scales. HP scale is on the left, torque on the right.

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Doug Chase
Chase Race
Custom roll cage and exhaust fabrication

Dennis,

I agree with you completely. The next step would be down in the area where the injectors sit as well as opening things up above and below it. The heads, as well, could really use some work just looking at them. My goal here was to eliminate just one bottleneck and hopefully raise the powerband a bit. I was hoping to make more HP by raising the powerband, and that wasn't much of a success, but the powerband did shift up about what I expected.

Honestly, my next step in this, and one I might pursue, is to use a carb manifold and an inexpensive Holley pro-jection 670. I have that on my Scout and the throttle response is unbelievable with the unit even though it's a very simple design (doesn't even have a MAP sensor). It still runs rings around an AFB or a Thermoquad, and you'd have to tune a Holley carb for a long time to get the results you can get with the projection in about 15 minutes of fiddling with dials.

But now we're leaving the realm of labor intensive and entering the realm of $$$ intensive. One would have about $1300 in a new manifold and projection by the time you figure everything up. It still might be worth doing, though, since my autocross class gives free reign on intakes and if the throttle response if it's anything like what my Scout has would be so sweet around the cones. (Not true for ITA or the road course events, though, Intakes are untouchable, but the mods we've talked about here aren't legal there either).

John Stricker

quote Originally posted by Dennis LaGrua: John, that's some beautiful re-engineering on that plenum. I wouldn't want to go that route though as I believe that there is only so much that can be gained from reworking this plenum. Take a look at the area inside the lower passageways of the middle manifold where the injector sits. Not much room there -right? You can port this area some as I did on my 3.4L but ultimately for my application, the turbo proved the solution. While your new design seems to have done much for the upper plenum I would say that the middle manifold will now become the prime restriction. What do you think?

Back from the dead.

THis is what your a/f ratio should look like. Of course mine is a bit rich but see as soon as the throttle goes wide open the drop to 12:1 is instant. It doesn't wait till 5500 rpm to get down that low like yours did alex. Your chip isn't any good. Of course you knew that but you need to do something about it. your ratio is way too lean up to 5500 rpm where it starts to go. I am suprised you haven't burned a piston being that lean at 5k rpm on that chip. See what custom chips do? You need a piggyback fuel computer. Plain and simple.

Other then mine being on the rich side thats exactly what they are supposed to look like. Nice and flat.

I am running a custom intake on a 2.8 with stock injectors and a stock chip.

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JM / SH

[This message has been edited by The Punisher (edited 08-13-2004).]

You got more data like that for the stock chip? I've been trying to gather data on the stock ECM a/f, and other info.