# C2 mk3 vr6 pro maf issue.



## BlownGinster (Jun 23, 2002)

Setup: 3.0 schimmel motor 8.0:1 compression, c2 pro maf software and injectors, precision PT61 turbo, modified stock manifold. stock + inline fuel pump. When getting into boost, in 3rd, 4th, 5th, I get a lean spike as soon as the turbo spools. It goes from 11.8/12.2 to 13.8 quick spike then back down to 11.3/11.5 to redline. It does this consistantly. Air fuel at idle shows 14.5/15.3 Never noticed it last year with the SRI I was running. I'm also showing an increase in EGT to 1500 in boost. Fuel pressure is consistant though boost car pulls hard and seems to run great. Checked intake for leaks, checked vacuum lines and everything checks out fine. I could see it going lean if their was a leak between the maf and the turbo, but I don't think it would go back to normal afr after the turbo spools. Any ideas????


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## 97VRT (Mar 6, 2007)

Are you running the stock FPR? what kind/size of exhaust?


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## BlownGinster (Jun 23, 2002)

adjustable rail mount fpr set @ 3 bar...just like last year. 3" turbo back, no cat or muffler.


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## TBT-Syncro (Apr 28, 2001)

bad injectors maybe.

have you verified fuel pressure under boost?


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## BlownGinster (Jun 23, 2002)

Steady fuel pressure via electronic autometer fuel pressure gauge mounted inside. I thought about the injectors, but problem seems too repeatable for faulty injectors. I did a run and logged a few parameters like throttle angle, timing btdc, maf reading, rpm, o2 sensor correction.


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## TBT-Syncro (Apr 28, 2001)

02 isnt used under boost, so it shouldnt be 02.

could be bad TPS

whats your 02 trim at idle? (it should be 1-2%)

you may want to try just doing a TPS re-alignment.

and your fuel pressure is raising with boost? i.e. 38psi at idle, with 1psi adding for each pound of boost you're making?


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## BlownGinster (Jun 23, 2002)

I already did a T.B. alignment. There is a rise in fuel pressure with boost, but not sure how much (was just making sure it didn't drop) I'm just puzzled why it's a quick lean spike, then goes back to being on the rich side. The only change from last year was the intake manifold. It did increase the torque and midrange considerably over the sri I was using. I'm going to try something I should've tried first. Turn the boost down to 12 (wastegate spring) and see if the it still reacts the same.............as soon as I replace the serp. belt that shredded on my logging run today:banghead: Here is the exel version of my log idling........I don't think this the correct O2 reading though.

Monday	24	May 2010	13:45:17 
021 906 259 H C2 Inc 2009.632P HS V03 

Group A:	'001 Group B:	'003 
RPM	Coolant	Oxygen Sensor	Ignition RPM	Mass Air Flow	Throttle Angle	Intake Air
TIME Temperature	Regulation	Timing	TIME Temperature
Marker	STAMP /min	°C % °BTDC	STAMP /min g/s	°	°C
0.23	840	70.5	-1.6	14.3	0.01	840	7.15	7.8	33
0.73	880	70.5	-2.3	12	0.47	840	7.08	7.8	33
1.23	840	70.5	-0.8	13.5	0.98	840	7.15	7.8	33
1.73	840	70.5	0	12.8	1.48	840	7.08	7.8	33
2.23	840	70.5	-1.6	12.8	1.98	840	7.15	7.8	33
2.73	840	70.5	-2.3	13.5	2.48	840	7.08	7.8	33
3.23	840	70.5	-3.1	14.3	2.98	840	7.15	7.8	33
3.73	840	70.5	-1.6	13.5	3.48	840	7.08	7.8	33
4.26	840	70.5	-0.8	12	4	840	7.15	7.8	33
4.77	840	70.5	-2.3	12.8	4.51	840	7.22	7.8	33
5.29	800	70.5	-3.9	14.3	5.03	840	7.15	7.8	33
5.8	840	70.5	-1.6	13.5	5.55	840	7.08	7.8	33
6.3	880	70.5	-0.8	12.8	6.05	840	7.08	7.8	33
6.81	800	70.5	0.8	14.3	6.55	840	7.22	7.8	33
7.33	840	70.5	-0.8	13.5	7.07	880	7.29	7.8	33
7.83	840	70.5	-1.6	14.3	7.58	840	7.15	7.8	33
8.34	840	70.5	-3.1	13.5	8.08	840	7.01	7.8	33
8.86	840	70.5	-3.9	14.3	8.61	840	7.15	7.8	33
9.36	800	70.5	-2.3	14.3	9.11	840	7.08	7.8	33
9.87	840	70.5	-1.6	14.3	9.62	840	7.22	7.8	33


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## BlownGinster (Jun 23, 2002)

That copy and paste didn't work very well.


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## BlownGinster (Jun 23, 2002)

Any other suggestions??


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## BlownGinster (Jun 23, 2002)

Havn't been able to play with the car for a while. I turned the the boost down to 10psi from 20. The lean spike is still there although not as bad. It happens while the turbo spools up then goes right back to 11.8-12.2. Fuel pressure increases with boost.....but after looking back at a video from last year, not as fast. I think I'm going to throw a new fuel filter in and see if it helps. If not, I'll start investigating the fuel pumps. On the bright side, the car is a blast even at 10 PSI. Anyone have other suggestions?


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## KubotaPowered (Jan 27, 2005)

I've noticed the same thing but the 440cc file did the same thing. I haven't lost any sleep over it. Hell, the blown VR with the 440's does it still


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## BlownGinster (Jun 23, 2002)

Thanx for the response. The car feels and sounds great, but I never noticed the spike last year........but didn't really pay close attention. It needs a fuel filter anyway


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## son of planrforrobert (Dec 21, 2009)

I'm with Kubota, my 440cc file does this, too. When I mash on it, it will dip for just a split second and then come right back up. Haven't lost any sleep, either 

Curious to see if the fuel filter is the culprit on yours, mine could probably use a replacement, too.


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## KubotaPowered (Jan 27, 2005)

AFRs will rise just before you start moving lots of air, as long as they settle down by about 4000rpms I keep my foot in it. The cars run so good, I gotta have something to monitor


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## therealvrt (Jul 21, 2004)

my customers mk3 obd2 vrt does the same thing, leans out around spoolup/peak torque then richens up
i thought it was the cat cams (256's) i put in it


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