dyno'd my car, numbers kinda screwy. Cam wrong? Turbine housing too small? HELP!

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fieroX

New Member
Joined
Feb 27, 2004
Hey guys, I dyno'd the fiero the other day. heres the graphs tell me what you see the problem to be.

dyno477.jpg


dyno4772.jpg


My cam is a hydraulic roller .512/.512 226/220 duration at .050", on 116 lobe separation 110 intake centerline. Ive been told my cam is mismatched to my combo. My engine is a series II 3800 that has been built up like a grand national V6, (somewhat). It has forged 8:1 pistons, forged rods, fully balanced. Garrett T66 turbo, .70 a/r T3 turbine (possibly too small and now a restriction?) Spearco water/air 2-230 intercooler. A guy mentioned a larger a/r turbine may yeild more upper rpm power, and adding a smaller cam (possibly going back to stock) would get the spool time back. Im thinking maybe a .440/.440 lift, 216/210 on 115 LC might work ok. What do you guys think? I know the technology for the series II's isnt really developed yet, but the turbo buicks of the 80's is still the grassroots foundation of our research. Thanks for any help.
 
Maybe I don't understand the problem...Looks like pretty nice numbers to me.
 
see how on the dyno graph the torque peaks then drops, as the horsepower peaks and stays somewhat level (actually drops some, then goes back up toward redline). The torque should go up, and flatline across the powerband, rather than slope off, as the horsepower keeps climbing toward redline. This is showing me some problems. IE exhaust restriction, intake restriction, something.
 
Maybe the heads just can't flow enough at high RPM? Most of the 80's turbo engines tend to stay well below 6k RPM unless its a stage motor with good heads.

You could be right on the T3 housing being too small, do you have any way of measuring exhaust backpressure pre-turbine?

Also, what engine management are you running? Perhaps you're not getting enough timing advance when it starts to drop off?
 
we were thinking the intake might of been maxed out, but there was some port work done to them. Gasket matching and bowl blending. Were really leaning toward the exhaust housing being too small. My exhaust was glowing after 5 seconds of WOT for god sakes! Engine management is done via an obd 1 computer system programmed by darth fiero. I have 60# motron injectors, and a zzp mini afc 2.0 a/f controller. I ran it on the wideband 2 weeks ago and got it set to 11.7-12.0 across the board. It runs excellent, just shows a weird graph. I expected about 540 whp out of it though, and it could of made that. Just trying to figure out what is going on.
 
Hmm, it seems like your horsepower would keep going down with RPM if your exhaust housing was really that restrictive.

Any idea what your ignition advance is in those areas (5,600 to 6,000 or so)?

ASSuming you're running 116 octane, I'd expect it to be around 28 degrees at a minimum to make good power. On pump gas it would probably have to be around 22.
 
looks a little spikey, series II ignition right?
what kind of fuel,timing, and boost are you running?

.70 exhaust housing seems ok, but dang, if its glowing she is hotter than donut grease!

got a EGT?

i think the graph is typical of most cars ive seen, the torque will dive down, but your HP needs to stay level all the way to max RPM kinda looks like a ignition problem????
BW
 
Im running about 17 degrees of total timing, on 101 octane unleaded. We cant run 117 or any leaded fuels for that matter, as the o2 sensors last about 30 seconds, and then are rendered worthless. Yes the car is an automatic. No GM FWD manuals in existance could handle this power level without blowing a differential through the side of the case. (trust me, already done it on a 13.80 car). were gonna try a larger turbine housing, and Ive already got a new cam in mind. Id also like to get some more timing going to this thing.
 
Originally posted by fieroX
. We cant run 117 or any leaded fuels for that matter, as the o2 sensors last about 30 seconds, and then are rendered worthless.
Click to expand...


This makes no sense?where is the o2 located?
 
Mine is about 18" downstream of the turbine outlet. On a stock L67, its located in the rear manifold maybe 6" away from the head. Trust me, these o2 sensors are very sensitive, and they will die a horrible death if exposed to lead. Been there done that, $75 bye bye! www.clubgp.com/forum <-- read more about it here.
 
Originally posted by fieroX
Mine is about 18" downstream of the turbine outlet. On a stock L67, its located in the rear manifold maybe 6" away from the head. Trust me, these o2 sensors are very sensitive, and they will die a horrible death if exposed to lead. Been there done that, $75 bye bye! www.clubgp.com/forum <-- read more about it here.
Click to expand...

Buy a Denso O2.
 
Mine has lasted through a couple of tanks of lead with no signs of going bad...Much better then Bosch's or Delco's, and just as cheap...Go to Sparkplugs.com to see if they have one for your application.
 
Originally posted by fieroX
Mine is about 18" downstream of the turbine outlet. On a stock L67, its located in the rear manifold maybe 6" away from the head. Trust me, these o2 sensors are very sensitive, and they will die a horrible death if exposed to lead. Been there done that, $75 bye bye! www.clubgp.com/forum <-- read more about it here.
Click to expand...

Geeezzz, I've had the same GM heated O2 in mine now for over a year and a half, with a LOT of 114 race gas run over it!!!!! Still working just fine!
 
If I am not mistaking a heated 02 doesent care if it is leaded or not, it is just the single wires that are temprimental. How do you like the heated compared to the single wire BTW
 
Originally posted by 85HOT-T
If I am not mistaking a heated 02 doesent care if it is leaded or not, it is just the single wires that are temprimental. How do you like the heated compared to the single wire BTW
Click to expand...

Well, heated O2's can be spoiled by leaded gas, it just takes a great deal longer than a one wire unheated unit. I gave up on one wire units over 10 years ago. Even my stock unraced 87 uses a heated unit.
 
Originally posted by 85HOT-T
Dave just out of curiosity, why did you quit using the single wire?
Click to expand...

For the same reason everybody else that runs race gas. It eats unheated O2's.
 
Put alcohol injection on that thing.

Your cam is ground like a turbo cam but its not installed like a turbo cam. Infact the way the cam is installed right now it would make the engine very sensitive to back pressure. You will probably need to retard the cam quite a bit to get it to act right. Retarding the cam 7 to 8 degrees from where its at would probably be a good starting point. This would put the Intake centerline in the 117 to 118 range. Theres basically two parts to running a wide lobe seperation angle turbo cam.

part 1 is that the wide LSA minimizes overlap.
part 2 is that you set the Int CL late by retarding the cam.

On the exh side this keeps the exh valve closed longer and helps the torque.

On the intake side this delays the opening and closing of the intake valve. The delayed opening helps to minimize the reversion in the intake manifold which kills power. The delaying of the int valve closing helps build top end power. The later closing of an intake valve usually hurts the bottom end alot and the midrange a little but the gain from reducing the reversion can more than out weigh this (depending on how bad the BP is).

HTH: Jason
 
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