Low Compression low vaccuum Running rich

[richmond82]

Before i get started i have been searching FAQ and Tech forums for some time to find an answer or info to lead me in the right direction. But each case is different and my build is much different than the ones i have been seeing when searching this issue.

Installed ARP head Studs and Power Enteprise 1.1mm Head Gasket. Had head machined. Timing MArks and CAS stab are dead on

Car is running Haltech PRO ECU
Toda 256 intake and exhaust cams w/10.5 advertised duration
Garrett 3076r .82 T3 with anti surge compressor
750cc injectors
haltech wideband,air intake temp 3 bar map sensor,Q45 Throttle Body, LS2 Coil Packs. Aeromotive FPR Aeromotive Fuel Pump -3am fuel lines 50mm BOV 38mm Tial Wastegate, greddy II spec b bosst controller

Everything integrated into New ECU harness by Wiring Specialties

Base Map from Haltech with adjustments

Car is getting 120 compression on all 4 cylinders - can the cam cause this ? the timing is on... can the thicker head gasket cause this. how do i ensure its not the rings ? leak down test ? adding 2 capful of oil then repeating compression test ?

Car is getting 9-12HG Vaccumm - checked all vaccum lines/intake manifold source. what else causes bad overall vacuum ?

Car is running extremely rich -

We set the overall fuel trim form 0 to -2 to try to even it out a little.
we calibrated the Q45 TPS @ o % and WOT
We calibrated injector dead times and flow rate
We calibrated the wideband (including fresh air calibration)
wE calibrated and linearized the ignition dwell times correctly for the coil packs

We have not changed the volumetric efficiency for the turbo

[BOOSTALOT]

wow this is very similar to what im dealing with as well, except i dropped compression on cylinder one only and am getting massive blow by. although im pretty sure my case is because of my piston rings. i have to do a leakdown test to confirm this.

i hope you find your problem. best of luck

[richmond82]

Originally Posted by BOOSTALOT

wow this is very similar to what im dealing with as well, except i dropped compression on cylinder one only and am getting massive blow by. although im pretty sure my case is because of my piston rings. i have to do a leakdown test to confirm this.

i hope you find your problem. best of luck

Thank you. Hit up realstreetperformance they have full ki minus the arp main studs for under 800$

[greenwood]

it's good that the compression is the same on all cylinders. the number is just a number, if it is within 5-10 on all that is good.

Could your starter that is turning the engine over be weak and affect the #?

as for low vacuum and all have you looked at other folks running your setup? boost leaks?

[BOOSTALOT]

Originally Posted by richmond82

Thank you. Hit up realstreetperformance they have full ki minus the arp main studs for under 800$

Will do man they are actually local so ill give them a call and see if they can help me out

[richmond82]

Originally Posted by BOOSTALOT

Will do man they are actually local so ill give them a call and see if they can help me out

fernando down there got me a invoice for
1029.95 for Manley H Beam Rods, CP pistons kit, ACL race bearings,thrust washers and ARP main studs !

Amazind pricing

[richmond82]

Originally Posted by greenwood

it's good that the compression is the same on all cylinders. the number is just a number, if it is within 5-10 on all that is good.

Could your starter that is turning the engine over be weak and affect the #?

Never thought of this ... does this happen ?

as for low vacuum and all have you looked at other folks running your setup? boost leaks?

yes i have cant find any boost leaks..... yet

[greenwood]

Weak starter cause low compression?

[richmond82]

Car is getting 120 compression on all 4 cylinders - can the cam cause this ? the timing is on... can the thicker head gasket cause this. how do i ensure its not the rings ? leak down test ? adding 2 capful of oil then repeating compression test ?


update to the above. I found ground on my battery wasnt making 360 Degree connection on the post. Ran a second Dry Compression test with all four plugs out and at Wide Open Throttle and got 145 on all 4 cylinders.

When running vac test before the needle was bouncing from 8-11 HG at idle. Now the Vac Test is steady at 12HG ?

can valve timing be that off to create this issue ?

[richmond82]

HMMMM ?


Steady idle (800-1200 rpm) Steady, low reading, 8-14 Small vacuum leak or valve timing off; could have low compression/worn rings (verify with a compression or leakdown test).

[richmond82]

How To Set Crank Angle Sensor (CAS) Timing on the SR20DET Engine

[tobroketobuildarealcar]

Check for a exhaust restriction that can cause low vac and comp numbers

Altho with your setup the numbers are not to far off considering the drop in comoression with your build and big cams wich reduce vac numbers any way

Your cams are in time to each other are they in time to the crank I have seen people get everything right but some how get one tooth off at the crank

And is your tune spot on for your setup that can also be a big issue

[richmond82]

Originally Posted by ZHANGWEN

Supply and demand. Simple economics. If someone posts it high and it sells then prices get pushed high

not sure what this has to do with the thread but you are correct

[richmond82]

Originally Posted by tobroketobuildarealcar

Check for a exhaust restriction that can cause low vac and comp numbers

Altho with your setup the numbers are not to far off considering the drop in comoression with your build and big cams wich reduce vac numbers any way

Your cams are in time to each other are they in time to the crank I have seen people get everything right but some how get one tooth off at the crank

And is your tune spot on for your setup that can also be a big issue

Car hasnt been completely tuned yet. Been working with Eric Gash at Haltech Tech to get the Base Map Adjustments made to be ready for tuning from Portland Speed Industries