ok iv got a weird problem, maybe im just on crack but i have never seen this before. so a friend of mine built up an ls vtec with p30 pistons, omnipower valve springs and retainers but stock valves and skunk2 stage 2 cams. anyways, we have been tuning the last few nights and made signifigant improvments from the gsr map. however when data loggging we are seeing 100% TPS but only about -5 to -6 in/hg at full throttle. all the other cars i have tuned im seeing about 0 on the vacuum gauge and like -2 to -.3 in/hg at 100% TPS when datalogging. also at idle its about 1500 rpm and i cant fix this. so it has to be a vacuum leak. but i have looked at everything and cant seem to find it. when i unplug the iacv it drops to like 400rpm. if its anything above 500 then i should have a vacuum leak but doing this simple test is telling me that its not. so my question is why are we not hitting full load. the air has to be getting out of somwhere between the TB and head. it also doesnt feel as fast as it should be. looks like were making between 150 and 155 whp on a race tune. hoping for about 180whp. any thoughts suggestions welcomed.

 

ttt

 

You are confusing the hell out of me.. what is -5 in.hg? wouldn't that be PSI?

At wot you should be at 0in.hg. like you said. If you have anything higher than that you have a restriction. Air filter??? Do you have a plugged exhaust?? Intake valve not closing. That is my three guesses.. Unless you have a S/C.

Are you around 18in.hg. at idle??? And your idle is the iacv if you unplug and it goes lower in rpm then that would eliminate a vac leak.

 

It could be caused by a leak or a restriction somewhere. What are you using to tune?

 

at wot the map is only seeing -5in/hg. i know its supposed to be 0. so there is something restricting it and its not the tps because im seeing 100%. i know its confusing. thanks for the ideas. maybe read it again slowly. sorry i was in a hurry.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thesmogman &raquo;</TD></TR><TR><TD CLASS="quote">You are confusing the hell out of me.. what is -5 in.hg? wouldn't that be PSI?

At wot you should be at 0in.hg. like you said. If you have anything higher than that you have a restriction. Air filter??? Do you have a plugged exhaust?? Intake valve not closing. That is my three guesses.. Unless you have a S/C.

Are you around 18in.hg. at idle??? And your idle is the iacv if you unplug and it goes lower in rpm then that would eliminate a vac leak.

</TD></TR></TABLE>

oh ya one more thing it does go lower at idle when i unplug it so it must NOT be a vacuum leak so something is restricting it. idle sees about 24in/hg. could be air filter, i guess. one more thing to think about. any other ideas?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">It could be caused by a leak or a restriction somewhere. What are you using to tune?</TD></TR></TABLE>

using crome to tune.

 

Just thought of another thing. Check your vacuum "Y"'s they have a limiter/smaller hole might be plugged.

So let me get this, the map is saying -5in.hg. what does it say with the engine off? is it correct? Have you checked this with a vacuum guage? If your readings differ then it has to be the map or these little limiter Y's

Now you have me wondering, I think the map is bad.

 

good idea, ill check what it logs when the car is off. but i dont know what you mean by the vacuum y's? the car was running 15.0 in the 1/4 with b16 cams and a gsr computer. now that its hot skunk2 cams and well tuned with slicks it only ran a 14.8. we were able to make about 30whp tuning so that means that after the head came off and put back on he lost alot of power.