4.3BV Over fueling - any pointers please ?

[TeGriffic]

Last couple of weeks I have noticed increased pops and bangs and the odd aroma of fuel.
At Griff Growl, I had the opportunity to put the car on the rolling road and asked for the air/fuel to be analysed - and below in the air to fuel ratio graph produced. The car was already warmed up when this was produced

There is a decrease in air intake evident as it drops from the 12/13 band to the 11/12 and as it does so the power appears to be dropping off.

Any pointers as to the order to things to try much appreciated.

Thanks.

Edited by TeGriffic on Tuesday 21st August 13:55

[coetzeeh]

Cant help you with any advice, but sheesh, I REALLY would have struggled to keep up with you lot to the Growl if your car was running well!

Thank heavens Hoover was not in a TVR!

[FlipFlopGriff]

Shawn,
Isn't this running lean at high revs?

Mine was over fuelling (a lot) which he reckons is good for another 15BHP but it runs sweet.

Did you run it to 8k revs??? I stopped him at 6k (256.2bhp)

Fuel mix just over 13 at 2k revs dropping to 12 at 6k.
I thought this was about right.
FFG

[dnb]

Mine was overfuelling too. We fixed it on the day and picked up another 15hp at 5000 RPM, so I would imagine you'd see the same sort of gain.

The graph above is showing VERY rich. No idea what's causing it though unless the AFM is over reading the airflow.

[TeGriffic]

It's definately knocking more fuel through to the exhausts, you cam smell it at times and I'm quite sure I'm using more at the guage. Acceleration is still very smooth so I discounted any failure in the ignition system - hence why I wanted to see what the rolling road said. I don't think he ran it up to 8,000, it didn't sound like he had.

The standard 4.3 before me came up at a theoretical 244 and I'm sure a BV should be knocking out more than a standard (this engine had a well known owner history by the way).

I was hoping it might be a common problem so easy to fix.

[Seasider]

The bottom scale on the graph is theoretical mph if they had run it to 8k you would've been picking the bits out of the tarmac

[FlipFlopGriff]

Grovers was 266 on a 4.3. Mine has a tad of history and 200k under its belt so 256 was a good showing at 6k and was still pulling strong. I'll get the overfuelling sorted and see waht we get next year. 270 easily I would guess. Still pulls so smoothly now though - shame about all the electrical glitches..
FFG

[350Matt]

could be a couple of things;
pressure regulator is playing up , or could be a blocked return line from the regulator get a gauge on there to check
or an injector stuck open, try a can of cleaner
or not firing on all 8 so a cylinders worth of fuel is going through, check ignition system
Or faulty water temp sensor, just fit a new one they're not much cash

Best of luck with it

Matt

[griffter]

My 4.3 did 240 running very rich too. I think the TVR map is set up to run very rich (reduces chance of detonation). Speaking to the crazy horses guys, these were the first TVR's they'd run on the rollers, so - with all due respect to them - the fact that nearly every car which ran ran rich may not be so unusual.

To sort it you can try tweaking the CO trim on the AFM, though I don't think it'll make much difference at high load. Otherwise, air flow restriction at high revs, or timing issues causing the ignition to not give a full burn of the cylinder charge. Engines are not perfect machines!

The fact that yours seems to have gopt worse recently does suggest something amiss though.

[TeGriffic]

Thanks for the replies. I think I'm going to have it back on a rolling road with someone who can go through the system properly and undertake some proper diagnostic testing. Does anyone know of anyone with a good reputation and who is TVR familiar around Essex or neigbouring counties that have been used by any PH'rs ? Else I'll be looking at Castle racing up in Towcester.

[Vixpy1]

To be fair, although in the strict terms 11 to 12 is rich for an N/A, its normal for a griff/chim to be running that kinf of afr. Don't look at it as a problem, more potential for some power to be made.