R53 low Compression but good boost figure… HELP
Thread Starter
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1st Gear
Joined: Oct 2024
Posts: 38
Likes: 7
From: Manchester
R53 low Compression but good boost figure… HELP
Today I took my R53 to the tuning shop for a custom map.
R53 Spec:
• ported & polished Cylinder
• 550cc injectors
• ph4 Newman cam
• 17% pulley
• bigger intercooler
• full milltek manifold & exhaust decat
• Denso colder spark plugs
onto of these prior to today, 0 miles ago it’s had:
• new timing chain kit
• new starter motor
• full service
• new snoot boots
• cylinder head gasket
• oil sump gasket
• rocker cover gasket
• auxiliary belt
• new crank case, oil pump seal, water pump seal, super charger seal/service.
•New exhaust and intake manifold gasket.
it is running good boost the shop says ‘no boost leak’ however the car is running about 30-50hp less than they expected. “However it runs very smooth”.
They’ve done a smoke leak test and a compression test, results were:
“Smoke test shown a leak at the PCV, and a small leak at the bypass and intercooler boots as well as in supercharger inlet. The boots are very common and such a small leak doesn't normally cause the larger issue we have. I've reseated the PCV pipe and that has stopped leaking. The inlet is a pain, even with a new seal these can leak, in the past we've used a sealant as well as the gasket.”
”Compression test shown 130/130/145/140 as 1/2/3/4. Which is on the low side, a good healthy one should be 150/170 all across. Both the low compression and HP loss might still point towards a timing issue.”
Apologies for the long post just want you to have the most informed guess at my potential problem.
All ideas that could fix this welcome! And thank you in advance for your help!
NathanR53
R53 Spec:
• ported & polished Cylinder
• 550cc injectors
• ph4 Newman cam
• 17% pulley
• bigger intercooler
• full milltek manifold & exhaust decat
• Denso colder spark plugs
onto of these prior to today, 0 miles ago it’s had:
• new timing chain kit
• new starter motor
• full service
• new snoot boots
• cylinder head gasket
• oil sump gasket
• rocker cover gasket
• auxiliary belt
• new crank case, oil pump seal, water pump seal, super charger seal/service.
•New exhaust and intake manifold gasket.
it is running good boost the shop says ‘no boost leak’ however the car is running about 30-50hp less than they expected. “However it runs very smooth”.
They’ve done a smoke leak test and a compression test, results were:
“Smoke test shown a leak at the PCV, and a small leak at the bypass and intercooler boots as well as in supercharger inlet. The boots are very common and such a small leak doesn't normally cause the larger issue we have. I've reseated the PCV pipe and that has stopped leaking. The inlet is a pain, even with a new seal these can leak, in the past we've used a sealant as well as the gasket.”
”Compression test shown 130/130/145/140 as 1/2/3/4. Which is on the low side, a good healthy one should be 150/170 all across. Both the low compression and HP loss might still point towards a timing issue.”
Apologies for the long post just want you to have the most informed guess at my potential problem.
All ideas that could fix this welcome! And thank you in advance for your help!
NathanR53
5th Gear
Joined: Aug 2003
Posts: 839
Likes: 225
Believe it or not, performance cams will often negatively effect compression tests. They're designed specifically to increase cylinder charging/scavenging at higher RPMs with a trade off of decreasing the same at lower RPMs. So when the motor is cranking via the starter, the RPMs are very low which makes the charging/scavenging low which creates a low compression psi.
What are the actual HP/torque numbers? What are they "expecting" your engine to produce?
What are the actual HP/torque numbers? What are they "expecting" your engine to produce?
Thread Starter
|
1st Gear
Joined: Oct 2024
Posts: 38
Likes: 7
From: Manchester
Believe it or not, performance cams will often negatively effect compression tests. They're designed specifically to increase cylinder charging/scavenging at higher RPMs with a trade off of decreasing the same at lower RPMs. So when the motor is cranking via the starter, the RPMs are very low which makes the charging/scavenging low which creates a low compression psi.
What are the actual HP/torque numbers? What are they "expecting" your engine to produce?
What are the actual HP/torque numbers? What are they "expecting" your engine to produce?
These were the results of the dyno
Dyno Graph
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