What would cause VTEC to drop off in power?
Thread Starter
Junior Member
Joined: Mar 2003
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What would cause VTEC to drop off in power?
What would cause a loss in power when VTEC kicks in with boost at around 8 psi? VTEC does engage cuz we can hear it but there is no real gain in power and from the dyno graph we have it really starts to drop and af/s are everywhere! We have come up with some reasons but I'd like to see what others might suggest.
1. Cam timing
2. something wrong with the cams, valves, valve springs or retainers
3. ignition timing (although it is pretty much stock, manually retarded it a bit)
4. oil pressure. It's tapped into the side of the block and I'm using a barb fitting (1/8) and a rubber line, so my oil pressure is at around 40-60, it ranges.
5. Turbine wheel could be too small. I used to have a .48 housing and wheel (stage 3 I think) and I replaced the housing with a .63 housing but kept the same wheel. The .48 housing seemed to choke at higher revs and with vtec, so I'm wondering if it's more the wheel?
I've pretty much ruled out fuel cuz we're running around 11.5 or so, so it's pretty rich as it is but still, we're really wondering why VTEC is not bringing in the numbers like so many of you out there.
1. Cam timing
2. something wrong with the cams, valves, valve springs or retainers
3. ignition timing (although it is pretty much stock, manually retarded it a bit)
4. oil pressure. It's tapped into the side of the block and I'm using a barb fitting (1/8) and a rubber line, so my oil pressure is at around 40-60, it ranges.
5. Turbine wheel could be too small. I used to have a .48 housing and wheel (stage 3 I think) and I replaced the housing with a .63 housing but kept the same wheel. The .48 housing seemed to choke at higher revs and with vtec, so I'm wondering if it's more the wheel?
I've pretty much ruled out fuel cuz we're running around 11.5 or so, so it's pretty rich as it is but still, we're really wondering why VTEC is not bringing in the numbers like so many of you out there.
Flaccid Member
Joined: Jul 2002
Posts: 571
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From: Seattle
stock fuel pump wont hold up. make sure you have an inline or upgraded in-tank.
cam timing IS an issue.
the turbine wheel shouldnt be an issue... it MAY become one near 7000 rpm as the .63A/R housing is still a bit too small for the H22, but a .82 A/R housing is too big, resulting in LONG spool up times. your best (and cheapest) option is to have the turbine fins clipped. should only cost you $100 or so from a local turbo rebuilder. if you dont have a turbo builder, i can have my builder do the clipping for you, and i can get you his info if you want it. BUT, this is not causing your current problem.
Unless you've got a new fuel pump, i'm gonna have to call it a fuel problem. the BTM you're using to control timing may also not be responding correctly, so double check it. also, read your spark plugs. it may also be a check valve defect, or even your turbo compressor side is improperly sized, so you're not flowing enough total air at pressure. (boost is not just about pressure, but also volume of air in CFM).
is the power plateauing at the VTEC crossover, or is it severely dropping off? EGT's would also be helpful in determining this problem, along with a list of all turbo and turbo related components in use.
just best describe your loss of power in the next post.
LASTLY.... your oil pressure is too high for the turbo. the motor needs 40-60psi for VTEC operation, but you need to step down the line pressure feeding the turbo. turbochargers need no more than 30psi oil feed or it will blow oil past the turbine seals (oil rings), inducing oil loss, coke, smoke, and premature failure.
cam timing IS an issue.
the turbine wheel shouldnt be an issue... it MAY become one near 7000 rpm as the .63A/R housing is still a bit too small for the H22, but a .82 A/R housing is too big, resulting in LONG spool up times. your best (and cheapest) option is to have the turbine fins clipped. should only cost you $100 or so from a local turbo rebuilder. if you dont have a turbo builder, i can have my builder do the clipping for you, and i can get you his info if you want it. BUT, this is not causing your current problem.
Unless you've got a new fuel pump, i'm gonna have to call it a fuel problem. the BTM you're using to control timing may also not be responding correctly, so double check it. also, read your spark plugs. it may also be a check valve defect, or even your turbo compressor side is improperly sized, so you're not flowing enough total air at pressure. (boost is not just about pressure, but also volume of air in CFM).
is the power plateauing at the VTEC crossover, or is it severely dropping off? EGT's would also be helpful in determining this problem, along with a list of all turbo and turbo related components in use.
just best describe your loss of power in the next post.
LASTLY.... your oil pressure is too high for the turbo. the motor needs 40-60psi for VTEC operation, but you need to step down the line pressure feeding the turbo. turbochargers need no more than 30psi oil feed or it will blow oil past the turbine seals (oil rings), inducing oil loss, coke, smoke, and premature failure.
GWAKS- Tech Geekifier
Joined: Oct 2000
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From: Hampton, VA
Originally posted by drift
stock fuel pump wont hold up. make sure you have an inline or upgraded in-tank.
stock fuel pump wont hold up. make sure you have an inline or upgraded in-tank.
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TRD japan ownerages
Joined: Jan 2003
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From: fort walton beach, fl
dude has it on the money...cam timing, and fuel delivery would be the main things id look for. you say you are running rich...that can be just as bad as running lean. check your plugs and see how that is. good luck finding it...
Thread Starter
Junior Member
Joined: Mar 2003
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Hey guys thanks for the replies and suggestions.
here are the dyno charts and bot hof them are at 7 psi:
This one is with VTEC (I did one run before with vtec but it was really bad that we shut it down pretty quick:
This is when we disconnected the vtec solenoid and I was able to rev to about 6 K:
Sorry about the pics, I think they may be a bit small, but we're also considering that we're running too rich because we peak out at around 185 ft/lbs and then the af/s go around 11''s :1 and then the power drops off, so take a look and tell me what you can conclude from these graphs. thanks. And yah, I know these graphs are pretty messed up!!! hahahaha
here are the dyno charts and bot hof them are at 7 psi:
This one is with VTEC (I did one run before with vtec but it was really bad that we shut it down pretty quick:
This is when we disconnected the vtec solenoid and I was able to rev to about 6 K:
Sorry about the pics, I think they may be a bit small, but we're also considering that we're running too rich because we peak out at around 185 ft/lbs and then the af/s go around 11''s :1 and then the power drops off, so take a look and tell me what you can conclude from these graphs. thanks. And yah, I know these graphs are pretty messed up!!! hahahaha
Thread Starter
Junior Member
Joined: Mar 2003
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Oh yah, and I am running an inline pump along with the JRSC FMU and I am not running any cam gears. I do not have a btm and I'm running pretty much stock timing. As for the check valves, I am not throwing any codes at any time so I'm pretty sure that they are working.