... low? VERY impressive numbers for that setup, and there is most likely some more left with some aggressive "intercooler" style timing.
Why would ANYONE think that those numbers are low for a Shortstack/rocker car?
drivetrain loss is much closer to 25% on these transmissions, so you can say about 335crank HP, but who cares... its still about 90-100 more than stock.
Where did you get "only 16 more than stock"? My friend had a tuned stock car put down 191WHP. The untuned pull was 182WHP. Technically its about 75 more than stock, considering you have a stock tune.
Note his curve is SUPER flat, which means he is making alot more power down low than most stock 3800's.
[This message has been edited by darkhorizon (edited 08-26-2007).]
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04:40 PM
AkursedX Member
Posts: 2890 From: Lackawanna NY Registered: Aug 2000
Before I went, I made a prediction of 260/325, so I was pretty close on my prediction. That being said, there is room for improvement. Above 4000rpm, my a/f's we're below 11 and by 4300, were below 10. Tuning some fuel out would make some difference. Hopefully next month I will have an in-car wideband operating and then I will be able to get a proper tune on it.
I didn't get any scans while they were doing the dyno so I don't know exactly what was going on except for my a/f's. I should also note that it was in the mid 70's and over 85% humidity on the run. I was kinda pissed with the weather. I plan on getting another run in the beginning of october. With cooler weather, and a better tune, I think 275/335 is possible.
As for scans: the day before I got in alot of scanning. It was 90+ degrees out and humid. I was seeing around .6-1.0* of kr and timing would go as low as 17.5*. Boost was running up to 10psi. Today on my way to work, it was 77* and about 30% humidity and I was seeing up to 3-4* of kr and timing would go as low as 15* on a couple of wot runs. Boost once again was at 10psi. I don't know how to explain that. Tonight I am going to drop to my 3.4 pulley to see what my scans look like with that.
------------------ '88 GT- 257rwhp 319rwft/lbs
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04:55 PM
AkursedX Member
Posts: 2890 From: Lackawanna NY Registered: Aug 2000
sounds like you seriously need me to tune that car, you should not be seeing any knock ever.... you most likely need a stock timing table though, you should only have 17 degrees at wot, at most.
with that setup, you dont need a wideband to get a VERY good tune on it. The wideband is only really needed for more agressive setups anyway, because an experienced tuner knows how to read fuel trims and narrowband averages over time, so it is still accurate.
[This message has been edited by darkhorizon (edited 08-26-2007).]
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06:05 PM
AkursedX Member
Posts: 2890 From: Lackawanna NY Registered: Aug 2000
It would be tough to do accurate tuning without a chance to do a 10-20 mile trip around town. The trick is dialing in the fueling before it goes into wide open, while wide open there isnt much we can do as far as tuning other than scale things based on narrow band results, but the thing is with stock cam profiles, we can scale it and see very accurate results.
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07:38 PM
Aug 27th, 2007
WhiteDevil88 Member
Posts: 8518 From: Coastal California Registered: Mar 2007
Where did you get "only 16 more than stock"? My friend had a tuned stock car put down 191WHP. The untuned pull was 182WHP. Technically its about 75 more than stock, considering you have a stock tune.
Define "stock". An L67 in a Fiero isn't "stock", so clarification is in order. Was it breathing through a stock 2.8 intake can? Stock 3800 exhaust manifolds? My best dyno run was 226/237. That was with a motor that had only intake and exhaust mods, along with proper fuel pump. The valve covers had only been off the engine to swap sides. No work at all had been done to the internals, and it was using stock pulley.
Horsepower is expensive, and every little bit does make a big difference in the Fiero. I also think that with the variety of modifications, there's more to come out of the car. But for the first trip to the dyno, I think you're going to have a whole lot of fun behind the wheel, Joe. And that's what it's about, not numbers.
PS, get anything in the mail yet?
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01:44 AM
Darth Fiero Member
Posts: 5921 From: Waterloo, Indiana Registered: Oct 2002
sounds like you seriously need me to tune that car, you should not be seeing any knock ever.... you most likely need a stock timing table though, you should only have 17 degrees at wot, at most.
with that setup, you dont need a wideband to get a VERY good tune on it. The wideband is only really needed for more agressive setups anyway, because an experienced tuner knows how to read fuel trims and narrowband averages over time, so it is still accurate.
The car was tuned for a 3.5" SC pulley. I should know because I tuned it before it left the shop (I did the swap). Akursed swapped the SC pulley out when he got the car home.
When Akursed went to the dyno he told me they didn't have ANY fans on the car or in the shop to move the air thru. Anyone that has ever been to a chassis dyno indoors can tell you that such environments are not the best on "warm" days even when multiple fans ARE PRESENT. I believe the low AFR numbers Akursed saw during his pulls were partially a result of this, coupled with the humidity factor.
The PCM cannot measure humidity directly. It has to rely on the MAF sensor to compensate for this -- in which case it does a poor job at best. Humidity + boost = over-rich condition. The reason why is because when you try to compress humid air, you end up with less space for the moisture. I have tuned numerous cars in the 8+ years I have been doing this, and I have learned time and time again that boosted engines are more sensitive to humidity than naturally aspirated engines.
Concerning the KR, 2 deg or less is what I consider to be "acceptable". In a perfect world I would like to see "0", but on the day Akursed dynoed it, considering the weather; I can't complain. When the car was here there was 0 KR. But, as I said earlier; since then Akursed has stepped down 2 pulley sizes on the same tune. Now the question was asked why did the KR increase with cooler/dryer weather? Well that's because cooler/dryer air is more dense, which = more available to burn; therefore the engine was making more power and building more heat in the combustion chamber. It was probably running a little leaner too, which brings me to my next point.
AFR (air fuel ratio). On boosted engines, the accepted “magic” number is 12.0:1. Well that's fine in a perfect world. However, we don't live in a perfect world so we need to take steps and plan for changes in weather and operating conditions. I have found that a good number on a boosted engine that sees street duty is about 11.5:1. If I see 11.2:1 - 11.7:1 while I am tuning, I usually leave it alone. That little bit richer AFR isn't going to hurt power output by any significant amount (dyno proven) and it will also keep the combustion process a little cooler = added insurance. Remember, we are talking about an engine with stock internals here. The last thing we want to do is tune it within an inch of its life. I have discussed this with Akursed and he agrees that the extra 3 or 4 hp we might find in a perfect 12.0:1 AFR isn't worth the chance of a busted piston ring land or any other damage that might occur.
Again, I have already discussed all of this with Akursed and he said he was going to ship me back the PCM for some tweaking.
-ryan
------------------ power corrupts. absolute power corrupts absolutely. Custom Computer Tuning | Engine Conversions | Turbocharging | www.gmtuners.com
[This message has been edited by Darth Fiero (edited 08-27-2007).]
the l67 is not a dyno queen its the power under the curve that makes all the diff. thats why if he llined up against a 500hp supra he would probably beat him in the 1/4 mile
