• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

Top swap not making power! Help

Steven Monteith

Steven Monteith

New member
I did a gen 3 top swap on my 2000 grand Prix with an xp cam and all the little things to go with it. Lifters. Valve springs. Ported heads. 42.5 lb injectors. Also on a 3.4" pulley. Its on the dyno and everything is reading good except for the power. Its only making 190 something horse to the wheels and a peak of 4.something boost. Timing is at 15 degrees with 0 knock. The boost reading was choppy going up and down during the pulls instead of a straight line like it should. He bypassed the boost solenoid to see if it would make a difference and it didn't. I suggested that the belt could be too big and slipping causing the boost levels being low and the boost levels going up and down. He checked and thought the belt was too big so they ordered a smaller one. Could the belt size cause that much of a power loss? What else could it be??
 


Not unless you're running some stupid huge belt.

The BBV should be dumping to the atmosphere anyways...it shouldn't be in the vac lines.

What are the injector IPW's?

AFR?
 
You have headers too (I'm assuming yes if you have the ported heads) You would hear if your belt was too big. I ditto blue. What is your AFR?
 
Yeah.

Get a scan from the dyno guy...AFR is Air Fuel Ratio, yes.

Also, IPW's should be less than 19~ honestly. If they are anywhere near that or higher they are maxed out. Which you shouldn't be on 42.5's with that setup.

Take a pic of the engine bay and post it...see how everything is setup and routed.

And by choppy...is it cutting out? Sounds like another problem all together.
 


On 15 degrees of timing...AFR 11.8-11.6. INJECTOR DUTY CYCLE AT 6000 rpm was 60%. MAF at 6000rpm was 220 grams per second. Boost max was 5.1 lbs. Average was around 4 lbs. By choppy I meant boost was going from 3-5lbs throughout the run. Going up and down
 


First question is it misfiring?

If no, then is the belt slipping?

If no, Is the BBV actuator closing during WOT?

Figure that stuff out first.

And the solenoid can fail separately from the actuator.
 
matt5112 said:
First question is it misfiring?

If no, then is the belt slipping?

If no, Is the BBV actuator closing during WOT?

Figure that stuff out first.

And the solenoid can fail separately from the actuator.
Click to expand...

No misfiring. I'm thinking the belt is slipping because of the boost levels going up and down like a roller coaster throughout the each run. Not sure about the BBV. how can I tell if its closing?
 
Remove the hose on the top and cap it off on the vacuum tree side. then go wot.

If you see more boost, then it wasn't closing and you need a new one.
 


matt5112 said:
Remove the hose on the top and cap it off on the vacuum tree side. then go wot.If you see more boost, then it wasn't closing and you need a new one.
Click to expand...
Which hose is that? There's 3 hoses coming out of it right? The guy doing the dyno bypassed it by connecting 2 of those hoses. Not sure which of the 3 though.
 
One of the first runs on the dyno the torque maxed out at 350 but the horse was like 170 with 10 degrees of timing and very low boost. The he hooked up the wires differently under the hood then both numbers were around 170
 
You must log in or register to reply here.
Back
Top