My 2.0 ABF Dyno run. Power seems down and AFR is high.

Maybe a small air leak and more evident at high rpm with engine inhaling harder?

Or becoming bigger air leak due to engine movement under load, ie rubber parts streching?

 

Sam,surely on k-jet, from my experience, if you've got ANY air leak the idle goes to pot.

If you had rubber parts stretching, ie air intake pipe - throttle body elbow, it would run terribly as sucking in unmetered air.If it had an air leak that bad, it'd whistle, wouldn't it?

Been chatting to Nige this week on the phone bouncing ideas around and it appears it runs 'ok' just feels gutless to what he's used to.

Obviously there must be a problem with the fuelling to show the AFR it did on test. Rubjonny, could it be a 'flow' problem with the fuel pump rather than pressure?

On ess-three's thread he's put a plot from a standard ABF lump up, 151bhp 12something lb/ft on a Maha set up.....

 

Main pump reservoir running dry would mean the lift pump is not up to task.
If the mechanical components are working as evidenced by the back to back testing using parts from Brookster and default, then it may be that at STD system and control pressure differential, the main pump is not flowing the require amount of fuel to achieve lambda and thus torque at the fix spark angle settings.

 

You just wouldn't hear that on the rollers with the other noise.

Nige, something I have just thought of, you've probably checked already, but are there any fuel lines kinked or crushed under the car at all?

 

I still (with my limited knowledge) think its to do with the cams. has anyone actually used twin KR exhaust cams on the ABF before and got good results? I know its been done on the 9a but aren't there some small differences between the 9a and ABF head?

I read somewhere that the exhaust valves were smaller by 1mm on ABF heads (27mm v 28mm) and valve lengths were shorter too, so if you have KR cams with less lift than ABF cams might this make a difference?

If you have the time and some standard ABF cams lying around you could plonk them back in to eliminate that problem.

Feel free to dismiss my suggestion if im being stupid

 

KR cams work fine in an ABF

Ian Vant's old mk1 had an ABF on k-jet running kr cams, and it did 173bhp on Dave Walker's rolling road. Bloody flew.

I think Nige has already put some ABF cams in it (possibly) to try.

He's deffo swapped the twin ex cams out and fitted stock kr's

 

All true Garry, i was just guessing really as i had a simmilar fault on my corrado

Rubber elbow had a fine slit in it, used to idle well and drove fine if driven gently but had problem when accelerating harder, must of been streching and leting air in

Was perfect since i replaced elbow

Still cant see how it can lack fuel if pump has constant pressure as Nige said on test runs?

 

Sam, fair enough if you've actually had that fault, I just thought any air leak on k-jet would cause a rough idle.

 

Only found it by chance, was cleaning 18 years of grime from all rubber couplings and came accross the split in the boot, it obviously only manifested it self under load and alot of movement which was ALOT due to shagged engine mounts

Just thinking it could be something as simple as that allowing unmetered air in and leaning mixture

Hope Nige finds the fault and saves this engine!

 

Same here

 

No need to warm up the warm up regulator. If you pull the air metering unit's flap to fully up, this will represent WOT, at max rpm, on a cold engine. In other words, the maximum possible fuel flow possible. If it was held a little down from this position, it would represent WOT at max rpm with a warmed up engine. WUR only affects CONTROL pressure, not SYSTEM pressure.

In fact, the only value of the injector test is to check for quality of spray pattern and an equal amount of fuel delivered by each injector. There's no real point trying to get quantitative fuel amounts off it. Getting fuel flow on its own is not so great value. You want fuel flow relative to airflow, in other words AFR. The wideband and AFR measurements does this much better!

For info, this is my AFR at WOT, 2nd gear accelerating from lower rpm to hitting the rev limiter at 7000rpm or so. You can also see MAP, which shows (approximately correlates to) how much the throttle was open too.

 

Also found these which might be handy. AFR vs control pressure:




AFR vs mixture screw adjustment (note how it makes almost no difference at high power):




A run thru the gears:

 

Cams are the std ABF cams now.

I am going to do the injector flow into a measuring bottle next week and will post my findings here, maybe somebody else has some figures of their own to compare ?

You wouldn`t hear a THING in that dyno booth ! it was so loud, even putting your ear to it wouldn`t make a difference.

I thought.
If I unplugged the lift pump and drove it, what symptoms would I notice if it was faulty, ie, would it start hesitating at high revs, or just do similar to what it is doing now?

Basically, there is voltage at both pumps, if I unplug the main pump the engine stops, if I unplg the lift pump, I couldn`t tell any difference with it idling, but didn`t want to take it on the road with that unplugged until i`d asked here.

I have looked CLOSELY at the pipes / hoses and really can`t see any splits

 

just reading pauls post, as the wur gives more fuel when cold, would it not be worth unscrewing it from the engine block whilst I try and find the problem, that would richen it up even when warm wouldn`t it ??

Obviously this is only a temporary suggestion to keep it rich for now.

 

Normally if the lift pump fails the main pump is really noisy, sounds like a chainsaw.

Mine failed once a few years back and it was very sluggish on acceleration.

 

You want to preserve the function of the WUR, ie lower control pressure at cold, higher once warm, so it fuels correctly at cold/during warm up, on all throttle and driveability settings, ie idling, part throttle, in traffic, etc. So simply unbolting it from the block is no use, it would simply give a 'bump' where it was too rich (part way thru warmup) since the heating element would eventually get it up to temp.

Neither is unplugging it, or a combination of unplugging and unbolting. This would reduce the authority of the control pressure swing, which would translate to too lean at startup and/or too rich once warm.

I guess the suggestion of ditching the whole K-Jet and going with EFI is looking fairly good, at the moment? Don't worry, its possible to set it up properly, you just need to be able to accurately measure the important things (CO at idle, AFR at part and full throttle). Also being able to measure fuel pressure is handy, since it saves the guesswork in setting things up sweetly. Once you have got the knack of knowing what sets what, a 'window' of good running will reveal itself, and you simply try different settings within here on the dyno, to get best power.