AFR irregularities

[Red October]

When the car was setup after the top end rebuild and the carb was re jetted the afr has been reading 11.9 on idle, with the mixture screw out as far as it would go. Over the last two weeks it's been steadily rising up till now 13.2. At about 3k foot down my afr is rising to 17 and when on boost 3.5-4k it settles down to 15. As fa as afr tuning goes I have hardly any experience :confused:

What would cause the afr to creep up? Is it time to get a updated fuel pump?

[Brigsy]

Possibly blocked fuel filter? Exhaust blowing giving false readings? 15 on boost is very lean.

On a well setup carb you should see 14/15 on idle, no leaner than 15 on cruise and 12.1 or richer i.e lower but no lower than 11.5 on full boost/full throttle

[Red October]

So should i give the mix screw a turn to get my afr to 14-15 without the fan on etc? Then obviously document the afr's on boost.

Im having the tank off on tuesday to fix a leak so ill give the filter a clean and make sure its ok in general, to cover that end.

I was under the impression the cars with significant peformance upgrades required the uprated pump at a certain point?

[Markey Mark (BD)]

Do you know whats been done to the carb?

[Red October]

Not really, blunty got my jets/needles etc and jutto fom ep motorsport fitted them!!!
The car at the time had a T28 instead of the current T25 if that makes a difference?
Jutto spent 2 weeks overhauling parts, porting and polishing the new head with multi angled/lapped valves to the spec blunty had so by my way of thinking im letting/forcing more fuel into the chambers............do i need a pump with a little more umph?

The reason i had the carb and head done was the car blew up the day befor the WGT rolling road day, it looks like i need a pro and a rolling road to setup properly

[BluntyR5GTT]

what fuel pump do you have on there atm ash? if its standard you defo need upgrade it

[Red October]

what fuel pump do you have on there atm ash? if its standard you defo need upgrade it

Unknown! havent got a scooby.

[BluntyR5GTT]

Id get an uprated one mate and try that

[Red October]

heres a really w**k video ive just made, this was taken just after i set the idle to 14.7. It looks like 13 on boost?!?!

http://www.youtube.com/watch?feature=player_embedded&v=p6JFk4TZMcA

[Mart]

Have you checked the FPR is working as it should?

[Red October]

Have you checked the FPR is working as it should?

talk about sense of humour lol! Concerning the FPR i HGAFCWYOA :laugh:

[Brigsy]

Have you replaced the fuel filter yet? If its blocked that will lean everything off? Check fuel pressure too

[Mart]

talk about sense of humour lol! Concerning the FPR i HGAFCWYOA :laugh:

FPR: Fuel pressure regulator.

[chezzer85]

How do you test to see if the FPR is working corrently? i want to check mine.

[rs250nut]

How do you test to see if the FPR is working corrently? i want to check mine.

With a fuel pressure gauge, base fuel pressure is around 5-6 psi if my memory serves me correct and should rise 1 psi with every 1 psi of boost, tee the gauge in between the main feed hose from the fpr and the carb.

[s3irios]

Your cruise is mega lean i see low 17s there. Boost is in "ok" territory, 13s are ok, not best but at least safe. It must be fuel filter, just change it mate it's 2 clips and maybe like 7 euros the filter(10ish pounds?). Don't put the white-semi transparent one as it is too small. Put an aluminium one bit bigger.

[TNT ANDY]

How does it feel to drive? I would imagine in the 17's would feel pretty bad. The gauge is all over the place and sometimes misses characters. Is the gauge / lambda ok? Can you try another unit?

[Red October]

UPDATE:

Well ive had a brand new phase 1 fuel filter and pump fitted, turbo gaskets, and put locktite on the M8 turbo bolts all round to get closer in nailing down why my afr's are bent.

I pick the car up at 6 and i can try again.............

The AFR gauge is like that on video because the innovate gauges are figure 8 lit numbers, the camera used shutter speed isnt as fast as the figure 8s movement.

The car is fine to drive atm, its a tiny bit hesitant just before it comes on boost. The main problem is taking your eye of the road because your cosistantly staring at the afr gauge!