13 * retard

[pontiacjeff]

Wheel horsepower is actual power put down to the wheels. It is less any drivetrain losses. A transverse mounted (FWD or Fiero) manual transmission will usually lose b/t 15-20% (I've found 18% to be closest). An automatic will be more like 25%. So the 178 you got is almost exactly 17%. My '95 GTP engine (auto) dynoed at 156, which is 25.5% of the 210 rating. The 190 you got is actually 229 at the crank, so you gained about 15hp over stock.

BUT, I bet if you look not only at the change in peak numbers, but at the at the rpms where the new peak occured, and the numbers above peak hp, you will see alot more than the 15hp. Dyno results can be deceiving when you focus too much on the numbers. I just built a 3" exhaust system on a Dodge Ram SRT-10 (Viper-powered) and it only picked up 20 peak hp at the wheels. BUT it picked up 40 horse power AT THE WHEELS at 6000, 800rpm above the peak. If you look at your graph again, I'm sure you'll see what I'm talking about.

I, too, used an angle finder to check the flats on the cam. I had a degree wheel, indexed the cams to the cam carrier, AND used the angle finder to triple check everything. Mine is turbocharged so I left the exhaust alone and retarded the intake 10deg. to reduce overlap and raise the rpm range.

[quantum110]

An automatic will be more like 25%. So the 178 you got is almost exactly 17%. My '95 GTP engine (auto) dynoed at 156, which is 25.5% of the 210 rating.

My 93 Stock Cutlass Dyno'd 167.6hp/171.8ft-lbs on a 95* day without a fan blowing on the engine...you may want to look into whats wrong w/ yours. Then again this can just prove how worthless dyno numbers are.

[DavidDeerson]

Jeff.I know what you mean about peak vs. usable HP.I did say that I picked up 10-11 PEAKhp at 5500rpm,but I did also say that the old reading at 6500 was down at 165-170 so I GAINED 20HP at 6500 from the old readings.This was from moving the power peak later with retarding the cams.

[DavidDeerson]

Also,I can't see how the weight of the Fiero will affect the needed mixture.I'm not accellerating the mass of the car,I'm accellerating the drum of the dyno.The weight difference will just change the rolling resistance of the tires,and I'm using smaller tires than most street cars(225/50-15 Hankook Z211R).The mixture above 5500 was below 9 to 1 at times,but mostly near 10 to 1. Now it stays around 12.5-13.

[Anonymous]

Look what happened last year when Mazda rated their RX8's horsepower high for advertising,then when magazines and new owners took them them to a dyno(since it seems every town has one)they found out the motor did not produce the HP numbers as advertised.Mazda offered to buy back the cars and changed the ads.I've dyno'ed many GM cars,and rarely ever seen the car make advertised HP,from a Impala SS to Quad4.

Actually the Mazda problem was over 8hp. Wouldn't make a difference to me, but to some owners.....

[pontiacjeff]

Interesting cam timing news. My 88 Turbo Grand Am (2.0 Daewoo DOHC head swap)... I used two .020"-thick head shims (above and below the head gasket) to reduce c.r. from 8.5:1 to 8:1. This advanced the cams 4deg. (as checked with an advance timing light). I assume this hurt top end power, but with no reference, it's hard to tell. It peaks at about 5600rpm. In a quest for more revs, (hell, the SOHC Pontiac head peaked at 6000!) I retarded the intake one full tooth, which is 7.5 cam degrees/15(!) crank degrees. Though, the net retard was only 11 deg. due to the thicker head gasket. ANYWAY... It picked up 20HP at the wheels at the same boost level, idles just as smooth, BUT DID NOT CHANGE THE PEAK HP RPM!?!?! The power curve looks exactly the same.

I would have thought 11 deg would have moved the power band, but no.

I guess the lesson here is it's the EXHAUST cam timing, duration, lift, etc. that determines the power band of an engine. My next step is to retard the exhaust one tooth/15 crank deg./11 deg. from stock and see what happens. My guess would be a real laggy turbo, which is o.k. for racing b/c it's easier to hook-up. I'll know later today... gotta go makes some money now. I'll post again tonight.

[dykz34]

You posted pics of the wrong motor... we wanna see the turbo 3.4L DOHC!

[pontiacjeff]

Ya, ya, ya, I know... I got distracted. The TGP didn't get finished for GPG, now I've lost interest. I work in shifts, I keep shifting from one project to another and never finish anything... sounds like a PSA for Adult ADD! LOL!

Anyway, the Daewoo 4-valve head is very similar to the 3.4DOHC. I think the info I gleaned pertains to this thread... so there!

(LMAO at that smilie!)

ANYway...

Here's the results, I think the same will show for any TURBO 3.4DOHC when compared to stock cam settings.

All runs in second gear, 7-8psi boost.

Stock (+4deg. due to thicker head gasket): Peaked 160whp at 5600. Very narrow powerband, 4500-6000.

Intake -11deg, Exhaust +4deg: Peaked 180whp at 5600. Gained 20whp from 4500-6500, 40whp at 7000, 57whp at 7500. Boosted quicker, more complete filling of cylinders due to reduced overlap.

Intake -11deg, Exhaust -11deg: Peaked 190whp at 6000. Lost 20whp at 4500, gained 15hp at 7000-7500. Same power curve as stock, just 500rpm higher.

So I gained 75whp with just cam timing!!!!!

I was limited by non-adjustable cam gears to one-full-tooth movement. One tooth is 7.5 cam/15 crank degrees. We have no such limits whith the 3.4!

Summary: For a street-driven, boosted 3.4DOHC, esp. manual trans, I recommend +4deg. exhaust, -10deg. intake. For full race turbo, I recommend -4deg. exhaust, -14 intake. The reduction of 10 or more degrees in overlap is critical for good use of boost. My '96 is set up 0exh, -10int. For the sake of science, I will probably put it back stock before I put it in the car. Then I can make these changes on the dyno for proof. Still, I stick by my recommendations for all you guys running turbos. Again... free dyno time in Atlanta for anyone wanting to test anything on the 3.4DOHC.

BTW, the end result on the TGA: ran out of fuel on the stock injectors (after bumping up f.p. from 43-55psi) making 240whp on 17psi.

[dykz34]

free dyno time in Atlanta for anyone wanting to test anything on the 3.4DOHC.

Wish I lived closer!!!!!!

[SappySE107]

Yeah, its too bad you are 12 hours away. Interesting to see the results with a turbo quad 4 though and the cam timing...and too bad they dont have our kick ass cam setup to change it however you want.

Id love to test out some head porting ideas on a dyno, but for now its all ass dyno and seeing how the computer reacts, at least until I get the flowbench running and try out some more changes. Cam timing, I could that all day long to see how it works out, and tune it every time to see what tuned vs stock programming with those cam changes as well.

[pontiacjeff]

I know this has strayed way off topic now, but I ran the car tonight. Retarding the exh. -11deg really killed the car on the line. I can't get more than about 5# boost on the foot brake. I used to get full boost!(granted, the old turbo was a little smaller.) And it doesn't hit 17psi for at least 100ft. The 60' times were the lowest they've ever been, hovering around 2.20's. Even going back to the old T-25 SOHC days, it would pull a 1.95-1.99. BUT, when it does boost up, the whole front of the car lifts about 1ft. and the car hunkers down and hauls a**! How's a best 8.72 @ 88mph?!?! The car weighs 3100# with me in it.

Back to cam timing... I think I'll run the exhaust back up the one tooth(+4deg adv from stock). It will boost quicker, make more average hp, might sacrifice a few hp up high rpm, but the car will drive much better. Lesson... keep the overlap TIGHT on a turbo!

[quantum110]

BTW, the end result on the TGA: ran out of fuel on the stock injectors (after bumping up f.p. from 43-55psi) making 240whp on 17psi.

Wait a second...Is this a real Quad 4? And why use a Daewoo head the Olds W-41 head is one of the most efficient heads ever built? I hope you don't take offense, because 240whp is a good numbe but I would think you would be seeing that at 14psi.

[RidgeRunner]

Not a quad 4.

I'm assuming it's the GM 2.0 SOHC as originally equipped in the turbo FWD cars, but with a Daewoo DOHC head swapped on.

[quantum110]

Ahhh...I see.

[pontiacjeff]

You are correct, Jon. And it's only a 2.0, not 2.3. The 240 is wheel hp, which is 320 at the crank.

The main point here is the cam timing... for boosted engines, retard the intake and advance the exhaust.