I have a Megasquirt driving the injectors and timing in my sorta D/Prepared or WC FC RX7. This past weekend I was using my car at Mosport in a Castrol Canadian Touring Car Race. The car would start and run okay. The lower rpm and lower throttle position bins were a little rich, but the car would pull through it okay. The car would pull hard at full throttle through 1st, 2nd and 3rd on most of the track. The car would detonate at about the same spot on the back straight no matter what we did with the timing in 3rd and 4th at about 6000 to 6500 and about 100 mph. We swung the timing from a max of 30 degrees to a minimum of 10 degrees. The car is a 1/2 bridge running on ITB's using Alpha N.

The car went well previously on a 650 Double Pumper Holley and using the stock ECU to control timing, but it is driving me nuts with this. I went through the complete data trace, second by second, last night with my crew chief Dave (who is an aerospace Electrical Engineer) to see what the heck was going on. The data gave me a ton of information but didn't show anything that was obviously wrong.

In a nutshell, the Air/Fuels stayed rich (with a few random spikes off the charts lean which could be sampling errors. They ranged from 10:1 to about 14.5:1. Where the car started to knock the car was in the 11:1 range. The timing stayed between 18 and 21 degrees max. The rest of the data was normal.

The car would pull very hard out of 5B and run cleanly to 9,000 rpm in second. I would shift to 3rd and pull hard to about 6500 and the car would start to knock. The sound was a very loud rattle (sorta like a bad rod bearing). I would lift, shift to 4th and as soon as I got on the throttle it would knock again. I would then coast to Turn 8 and the car would handle full throttle in 4th or a shift down to 3rd and pull through the corner fine. It would also pull 3rd down the front straight with no issues. There were other places on the track where it would pull hard or burble rich, but I am okay with that as it just means that I have to lean out some bins.

We initially thought it was a fuel pump issue and the car was going lean, but the Air fuels look okay, but a bit rich. If it was a fuel pump issue I don't understand why it will take a hard 3rd gear run down the front straight, but not on the slightly uphill back straight. Is it the incline, the difference in fuel requirements by the uphill, some weird timing scatter or a weak coil. I don't want to go to a dyno until I get this issue dealt with.

Gotta figure it out as this is a tough one. Any advice or help by anybody would be appreciated.

Regards,

Eric Nummelin

 

The car would detonate at 6500 at 10 degrees?
Have u checked with a timing light what the timing is at 6500?(2-stroke light)
How much gas is in the tank what kind of pick up is in the tank?(may be the gas is running away from the pick on the incline)!
You do have a wide band for the air fuel readings right?
post you're msq and the data log

 

Try increasing split at that point.

 

After much examination and running we have tracked the problem down. I didn't believe it when I saw it the first time and discounted it as a brain cramp. I have searched numerous threads and not found an answer.

What is going on is that at idle the timing is set at 2 degrees advanced. You rev up the car and the timing swings to about 5 degrees advance, then reverses itself and ends up at about 30 degrees retarded. I saw this at the track and tried to compensate by advancing the timing by 10 degrees and retarding it by 10 degrees and only ended up screwing up my idle timing with no change in higher rpm running.

I got Dave to finally understand what I was seeing and he scratched his head and looked into the setting until he came across the dwell setting. It is set at 4 ms and he felt that the dwell setting was delaying the spark too far and the effect multiplied as the rpm built up. So I had him change the dwell to 0 ms and see the effect. We ran the car again and for the first time the timing advanced as the rpms built up. The only problem now was that the timing advanced to well over 30 degrees, when we had it set to a max of 20 degrees advance.

I believe that we are on the right track and that the dwell needs to be closer to zero, but with some dwell maybe 1 ms. Does this sound like it makes sense? Is everybody else using 4 ms and we are just wrong. Can we just be adjusting the dwell and it is acting like a bandaid for another issue that I don't understand yet. I think we are getting close and I am very excited about finally being able to run the car hard.

The coils and ignitors are stock S4 units and the CAS is a stock S4 one as well.

Any help is appreciated.

Eric

 

You're not running with spark output inverted are you?

 

First, I want to apologize for the delay in responding. We took MuyThaibxr advice and checked if the spark was inverted. It was and we changed it and voila the timing was correct. After getting this done there was still a ton of setup that still needed to take place.

We fired up the car and no matter what we did we couldn't keep a consistent tune in the MS. It would run fine, sometimes great, then we would shut it off and the next start was a crapshoot on how the car would run. 98% of the time it would revert to some previous timing or fuel MAP and we would have to set the car up again. It was driving us nuts!!!!

I am very lucky to have a guy like Dave to do the work. He is very well qualified in electronics and is very thorough in his process. We ended up going back to square one. We checked the CAS, the Coils, ALL OF THE IN CAR WIRING and the injectors with no obvious issues. Finally Dave decided to perform a circuit by circuit check of the MS. It took him over 8 hours, but at the end he tracked it down to the circuit the drives the injectors and a few of the connections that may have been damaged by an voltage spike we had the first time we started the car.

Forgive my ignorance on the exact parts, but according to specs the voltage firing the injectors was supposed to be 5Vs, but we were getting an erratic 1.5 to 3 volts. Dave pulled the piece, bought a new bit and soldered it back in. We loaded a previous known good MAP and the car fired up perfectly and ran crisply, just not very well.

It took some tuning and playing with the ignition timing but we got the car to work very well in the driveway in neutral. We then decided to finally go back out for a test day.

We got to the track and the car started well and as it warmed up the car started to run leaner and leaner. WTF!!!!! Not again.

I got heated and threatened the car with having the Holley re-installed and binning the whole thing and Dave was searching the many varied tuning tools for a clue. Finally the answer hit us like a ton of bricks. We were tuning the car in the driveway and not able to rev the car very high due to noise issues or run it for more than 20 minutes at idle. The issue was the cold start enrichment which was set to 85 degrees celsius and adding a 15% enrichment. Until the car got really hot it was getting lots of fuel and we were leaning it back to run clean. Once it got hot, the enrichment turned itself off and the car went super lean. We turned back the enrichment to a max of 50 degrees celsius and richened up the total map by 15%. The car started and ran great. I blipped the throttle a few times and it sounded good, but the Air Fuel was showing a lean drop about 4000, so rather than change the fueling requirement we tried lowering the secondary injector transition to 3000 rpm. We felt that with the 4 ITB's we needed more fuel in the outer runners as the different port timing might be causing a very lean spike in the chamber.

The car ran freakin great. It now starts like a stocker. Idles at 1,000 rpm and has basically smoothed out the bridgeport lope. The car has enough torque to spool the back tires at any RPM above 5000 in second gear. The throttle response is like an F1 car and the overall power seems to be very strong. We do have a small issue with the car running out of fuel above 7500 rpm as we have exceeded the ability of the stock FC fuel pump to meet the fueling requirements on longer pulls, but for short bursts WHOO WEEE it pulls hard. I was leaving over 30 feet of RA1 rubber out of a few corners until I started peddling it. The car would pull to over 9,000 rpm at 3/4 throttle, it just wouldn't pull at full throttle over 7500 before it would start to go lean (A/F's would rise from 12.5-13.5 range to over 16.1) and start to detonate a bit. Removing timing didn't help and adding fuel didn't help. Justa mechanical issue, but a good one as it means we are making more HP than a stock NA pump can handle. Water temps remained rock solid at 180 degrees F and oil at 155 F on a 90 degree F day in all second and third gear running.

I love the way the car runs and we wouldn't have got here without a lot of help. Thanks to everyone and you can count me in as a satisfied MS user. If I had to do it again, I would have gone to the Alpha N earlier and maybe got the car running on a stock TII intake first, then swapped over to the ITB's.

Thank you to everyone for your help.

Eric

 

That's awesome news Eric! A great read too. Nicely done

 

man i just loved reading about the car being on the track lol. awesome to hear about it coming together, hopefully i can reach my goal of learning to tune MS to its max.

have you dyno'd your fc ?

 

I'm going to check this in my settings as well, because I've been having the EXACT same problem with my timing and detonation issues.

 

Hi There

I found that the stock fuel pump works fine the only up grades that I made was to increase my fuel line to 3/8" put a large in line fuel filter, machined out my fuel rail for flow set my fuel pressure regulator to 42lbs and used my old fuel supply line 5/16" to return fuel back to tank. Fuel pressure remained at 42lbs at all RPMs and no issues to 9000 in 4th as well. Up hill or down. Post some photos of your oil cooler lay out those are great numbers for what the out side temps are. Are you drawing temperature out of the pan or after the cooler? Mine is allways 220 off the oil pump.

Sound Good Race Hard and Safe

Best Regards
RX2 Racer