3" exhaust = POWER!! - Page 5 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 12-22-2004, 04:51 PM   #41
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Quote:
Originally Posted by dbtk2
So when did you put the PCM in??? The first pull says 3.4 pulley only. Second pull says 3.4 pulley, 1.9 rockers, 3" exhaust. Yet, your sig says you also have a DHP!?!?

Shawn
Actually Dave lives near me. I drove over his house and he came up with his program which he just flashed into my O.E. PCM. This guy knows his SH....stuff. There is no way I'd allow any other tuner to touch my car. Just my personal opinion, but my experience is what I gauge this on.
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Old 12-22-2004, 11:35 PM   #42
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Quote:
Originally Posted by Dans2002bonne
Quote:
Originally Posted by dbtk2
So when did you put the PCM in??? The first pull says 3.4 pulley only. Second pull says 3.4 pulley, 1.9 rockers, 3" exhaust. Yet, your sig says you also have a DHP!?!?

Shawn
Actually Dave lives near me. I drove over his house and he came up with his program which he just flashed into my O.E. PCM. This guy knows his SH....stuff. There is no way I'd allow any other tuner to touch my car. Just my personal opinion, but my experience is what I gauge this on.
I know dave pretty well too. I've personally driven his '02 Z28 (across a parking lot, but still, not very often someone gets to drive an 11 sec. car). We went to his house to get the GTP PCM and the SSEi PCM flashed. I agree, he does know his ****, and damn can he tune a PCM. Not very many people hand you their Tech 2, and say, "go drive the car, look at the shift points in MPH and rpms and tell me what it is so I can find out how it needs to be changed." Then once he changes it he says, "go do it again and see how much better it is and if it still needs to be changed, and here take my performance meter too and see how it runs while you're at it." Needless to say, we did quite a bit of driving around while we were there, making sure the shift points were right. Even though we already had a DHP in the GTP, getting it custom tuned woke it up like you wouldn't believe, and he didn't even do it on a dyno! Thats why we brought the SSEi out and had one put in it as well, and it was a completely different car after that.

The reason I ask is because you started out the post with "just got the car off the chassis dyno," which I would take to mean, today or yesterday or pretty recently, and then you say originally it had a 3.4 pulley only. Then you say on the pull that you just the car off the dyno from, it had the 1.9 rockers and 3" exhaust added. And your sig says you have the pulley, rockers, exhaust, and PCM. If this just happened, then that means that you somehow squeezed the PCM in there between the time you dynoed and the time you post this, which, by the sounds of it, doesn't seem like a lot of time. So the story isn't lining up somewhere.... To get straight to the point, I was trying to make sure that you didn't throw the PCM in there between those two pulls or something, and maybe you forgot about it or something.

Shawn
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Old 12-23-2004, 06:00 PM   #43
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Hey there. No, neither pull was done with the program in the PCM. The first time I had the car dyno'd, was last year right after the pulley install. That is where the first numbers are from. After this everyone was searching for a DHP for the SSEI'*. Well I ran into Mr. Buckshaw. So, he did his thing. Not too long ago my car developed a shudder at free way speeds slowly accelerating from 65 up to 75. Afraid it was something inside the tranny, I took the car back up Daves way, we reflashed the car back to stock, so I could visit the dealer. As of today I have not gone back to see him as I let him help me at his convenience because he is probably the best business guy I've ever dealt with. So this in turn is how the two dyno pulls were both done, by chance, without any program outside of factory.
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Old 12-23-2004, 07:32 PM   #44
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Sorry to chime in again so late in the discussion... I just wanted to comment about the question of driveline hp loss. I would agree that extra power could be lost due to increased strain put on components, but it wouldn't increase proportionally to the mechanical loss of the stock setup. Sorry if that'* a ten-dollar sentence, but I'll try to explain myself. The amount of power lost due to the mechanical nature of the stock driveline might be 40-50 hp, whereas when you run a 400 hp motor you might lose 60 hp in the driveline due to mechanics + extra friction. Yes, you're losing more power, but power lost to friction isn't in the same ratio as percent of stock engine power compared with stock wheel hp. Confused yet? Lol, sorry. To make a long answer short, I don't think you can add mechanical power loss to frictional power loss and come up with a reliable ratio that can be used on any power configuration. I don't want to ruffle feathers here, I just don't see how it could be possible. We can start another thread if we need to. Sorry for the hijack!
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Old 12-25-2004, 09:37 PM   #45
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i get what you mean bignews1. We need a tranny expert to sort this all out.
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Old 12-26-2004, 05:49 PM   #46
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Let'* start with the exhaust. Backpressure is bad the end. If the exhaust is too small it will not flow enough volume and the waste gasses will not all make it out of the cylinder during the exhaust stroke. If the exhaust is too big it will not maintain sufficient velocity (the gasses will stall) again resulting in poor evacuation of the cylinder.

There are too many variables affecting this for the average enthusiast to calculate so, the only way to really tell is try it or trust the reputable after market manufacturers.

On to the transmission. Drive train losses are a percentage and they are not constant.
All streetcars have helical cut gears (manual and auto) to reduce noise. Most racecars have strait cut gears to reduce friction. Helical gears generate axial thrust in proportion to the angle of the helix and load on the gear set. Most manufacturers and tuners use a fixed percent loss of 15% to 22% to simplify things. It'* not exact but close enough for most real world uses.
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Old 12-26-2004, 06:00 PM   #47
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the only way to figure out the exact loss of one of our transmissions would be to take it and dyno it on the car, then dyno just the engine. THen you increase the power, and do it again. And repeat.
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