MFI Pump - Open Heart Surgery

[dicklague]

Hope you get it fixed soon. Good luck!!

[Eddyvdw]

Thanks guys.

Dick, will figure out the non picture option asap.

Below graph is of a run today. Accelerated to 6000rpm, changed gear and at tried to keep the engine at 4000 rpm under load.

Your votes please.

Ed

[Eddyvdw]

Now a run uphill. The first part was a bit winding so I had to accelerate/de-accelerate. Then uphill at constant rpm/speed. (6795 onwards). At the end of the hill I accelerated to 6000 rpm.

What I noticed is that at idle and accelerating the AFR is around 14 (sometimes a bit over). When driving at constant speed (think you call it cruising) the AFR drops to 11-11.5. Uphill at constant speed it's a bit better at 12.

Btw, we went for a tour yesterday and today to the North of Czech. My friend in his new Audi A4 Cabrio didn't want me to drive in front anymore because of the horrible exhaust smell.....

Ed

[dicklague]

It does seem a bit rich. I will leave it to the experts to answer. I don't pretend to be an MFI expert.......I am a Wego IV expert and it is good to see you have it working well.

Looks like you have mastered the mspaint trick too.

On my car I have removed the warm up bi-metallic stack and put in a manual adjustment. There is a photo a few postings back on this thread. This lets me change mix across the whole range of RPM.

Nothern CZ........we shot a race in Jablonec nad nissou near Liberec a few years ago. Interesting country.......

Good luck tuning....wish I could be of more help...

[304065]

what exhaust system?

[Eddyvdw]

All is stock.
Engine is 2.4E.
Pump calibrated by Mark Jung.
Followed all steps of CMA.

Ed

[Eddyvdw]

I turned the main rack adjustment 1/4 turn CW to lean it out a bit.

The reading is much better now. Uphill to 7000rpm reads around the 15-16 AFR mark.
Idle is just below 14.

What still annoys me is that while cruising the AFR is around 11.5-12. I suspect this requires a bit more sophisticated adjustments.

Ed

[dicklague]

even though 14.6 is Stoichemtric best power and safety in an air-cooled engine is in the 12-13 range.

Idle looks OK, but that is a bit lean for high RPM.

Be sure the free air calibration is good. Let it sit over night and adjust to be sure your readings are accurate.

[Eddyvdw]

Thanks Dick.

This is the reading with the part throttle half turn CW. The car feels more rough. I made a full acceleration on the highway to 150 km/hr. Idle is a AFR 14.

Jus wondering, the sensor is only in the left HE. What is the right cylinder bank is way of?
Although leakage was ok, what if one of the cylinders doesn't work well, will that influence the reading?

Thanks for helping me to understand the engine and AFR.

Ed

[210bhp]

Dick

I am reading this long thread over and over to get to grips with the sensor technology in preparation for doing this myself. Does the 'dual sensor' which is available allow you to take readings from both HE's? Or is the dual sensor measuring two different things from the same HE hook up?

Regards
Mike

[dicklague]

The dual setup comes with 2 wideband sensors. You can mount one in each bank at the point where the individual header pipes come together. The kit comes complete with 2 sensors wiring etc.

I am running a Bursch and the 2 banks go into one pipe. This is where I welded in the 18mm bung for the sensor I actually put bungs in each bank and one after the muffler for future use. You can see one in the back ground with a plug installed. I have actually never tested any of these other locations yet. see photo below.




The sensor wire goes through the rear engine seal and comes out in the engine compartment.




I removed my non-working clock and installed the head unit in the dash at that location. Use either the extension wire kit or make your own. Our host carries the extension and both the WEGO IV and the dual.



Here is the final install. The digital gauge on top is a digital volt meter. The one below is the AFR. I the switch to the right allows you to turn off the voltmeter so as not to distract or confuse with quick glance AFR readings. It is off in the center position. In the lower position it read battery voltage with the key off. This lets you check the charge even before you insert the key. The clock position gives you a good clean look at the AFR readings with taking your eyes too far off the road.

The mini USB plug is for downloading the up to 2 hours of AFR data.

[dicklague]

This gives you and idea of the almost Mil_Spec layout of the Wego IV. Very high quality components and very high quality construction and design.




This is the front panel with USB connector and free air sensor adjustment above the connector. Over on the right is a little eye that adjusts the AFR lighting to dim at night.

[210bhp]

That is great info and pics Dick. Thank you very much.

Regards
Mike

[dicklague]

Thanks. It is a great addition to the car. I built a unit into in where the clock normally is located. Here is more detail on it:




Scotland......my wife's family are MacDougals from Skye.

[210bhp]

Edit
Dick
I took this last post of mine off line and put it in your pm box. It has really nothing to do with MFI and I don't want to interrupt/deflect this great thread off course.

Regards
Mike

[Ducman]

First off - wow to this thread. Thanks to this I think I can now dig in and tune my MFI myself.

So this is the first post - base line stuff. Some of you may have followed the recent build and delivery of my 2.8SS over on the engine building forum. Henry at Supertec did a fabulous job. Now it's in my hands. Attempting to tune via timing, and the two basic external mixture adjustments failed. Reading this thread several times, attempting to understand how MFI actually works...I really do think I have a pretty good idea of what is going on and what I need to do.

I'll post more engine specs later but key is that it is not stock and the MFI is a red top race type conversion without any of the street type, starting, warm-up and decel cut, regulating devices. There is a lever type manual enrichment for starting.

I am using an LM-2 and my only dyno is long straight undisclosed rual roads

Actually driven in most any sane street manner it works pretty good albeit a little cumbersome to cruise out of the subdivision. On the track - do not have nealy the response or top end I expect + temps rise very quickly. Autocross is very difficult due to poor WOT low to high transition.

The LM-2 says: I am extremely lean in the low to mid RPM WOT range (AFR 18+) and extremely rich in the mid to high RPM WOT range (AFR <10)

I think this corresponds exactly with my driving impressions - furthermore, because of this imbalance any attempt to tune with the part load adjustment only exacerbated the condition at one end or the other i.e. overall leaning for top end power completely distroyed low end and vice versa.

To the black and white screws I go! I'll keep you posted.

Don

[Jeff Higgins]

Don, that sounds like a far greater range of A/F ratios than can be taken up with any screw adjustments. If you go through this thread in detail, you can see where I (or we) learned that the screws are not really meant to change the fuel delivery rate per se - they adjust how far aft the space cam travels (as the flyweights open) for any given rpm. They are only used to fine-tune the fuel delivery rate, not to dramatically change it. In other words, I initially thought they provided a somewhat linear adjustment, where turning them in more always meant the mix was getting richer. Not so. The mix can get leaner by turning them in, or richer, depending where the stylus is riding on the space cam to begin with.

In the time since I started this thread, I somewhat reluctantly arrived at the conclusion that the only real answer for my motor was a custom space cam. So I reground one of mine. It was then, and only then, that I was able to narrow the A/F ratio spread to an acceptable range. And, before I started, my spread was only about 2 points - nowhere near what you are looking at. So, in llight of that, this might help:

MFI Open Heart Surgery III - Reworking the Space Cam

Mine was rich on the bottom and lean on top - the opposite of yours. You may be able to rework the idle rpm / throttle wide open area of the space cam down a bit to narrow the gap, making it run richer there without affecting anything else. Maybe...

[Ducman]

Thanks for chiming in Jeff. I was hoping you would still be following this thread.

I recognize my starting point conditions appear to be opposite of yours but I really don't consider the range to be all that much greater. If I can close the range anything close to what you did prior to looking at a custom grind I will be very happy.

Curious about the rpm range effect - my engine is intended to spin ....6000-8000 rpm is the targeted fun zone.

Made first set of adjustments last night - appointment with the lm-2 and asphalt dyno this afternoon. We'll see.

Don

[Ducman]

Well - in general I was turning black screws in to richen, white screws out to lean and main rack out to richen overall. Main problem was that I could not seem to get rid of lean condition on wot low rpm. This caused violent bucking at wot low rpm. I switched mufflers from bursch to M&K. With the m&k the issue now manifest itself as lean at nearly all part throttle positions and pretty consistent but rich at nearly all wot positions. I then started leaning both white and black screws while richening main rack. This did help. It is drivable but not as crisp as with the bursch. Considerable adjustment has still left part throttle lean which I consider annoying but not dangerous. Thinking about going back to bursch and try more aggressive amount of clicks to wot low rpm to take care of initial lean.

My lm-2 crapped out on me-so I'm without until I get it fixed.

Don

[Ducman]

Ok some interesting stuff,
The top end was really much better with the Bursch so I decided to put it back on and see if I could tune out the low rpm wot lean condition. Mind you I am still working on feel as my LM-2 is not yet back from repair.

I got aggressive with the black adjustment screws toward rich and it helped a lot. Both white and black adjustment screws are now about 15 clicks out from full in rich. I also lengthened the pump rod about 2mm to richen the mixture under all conditions. I've also been playing with another adjustment - which I understand is normally reserved for atmospheric pressure compensation on a stock mfi. On my race modified mfi this system is replaced by a regulating bolt. I've richened this a bit. The end result is that it now transition quickly and steadily from 2000 rpm up. 5000 up it has snap response to wot and pulls to 8000 like a scalded ape. Idle is steady. Steady cruise at most rpm range is very good except 3500 rpm and below. At this rpm range it will initially be fine but after a short while (15 seconds) it will begin to surge....not sure if this is lean or rich....really need the lm-2 back.

My engine appears to be sensitive to the exhaust which could be a combination of mfi and cam (dc80).

Don