Where do I start? I'll give this my best explanation leading up to problems I've been having. We're in the process of tuning the car I've been working on for what seems like forever. It's a Honda V6 set up to eventually run the MOD class in NSCRA. I initially started with the idea of running gas, then changed over to methanol. Because of that decision, I up the injector size to siemens injectors, 220lb. It seemed they ran out at 19psi boost, 95% duty at 100psi fuel pressure. So I went for the gusto and put in Moran 550lb injectors. Car idles fine, now injector is at 80% duty at 85psi fuel pressure with 27lbs of boost. Target boost is 40-50 and these injectors at the rate I'm going will puke out. How can that be?

The real problem starts at 6500rpm, cylinder 3 starts to wig out on the EGT. We have the motor a little rich for safety, all egt's are in the range of low 900's. the egt on cylinder 3 starts to rise at 6400 and by 6500 that egt is at 1000. At that point it nose dives over like Niagara Falls with the engine sputtering. Boost is constant at 27psi, fuel pressure is constant at 88psi. When I do a pull at 20psi boost, I can carry the rpm right up to 7700-8000 with no problem.,, put 27 in it and kaput.

I changed the plug, swapped coils and even swapped cdi boxes thinking it may be ignition related, it does the same thing at the same point everytime. The only other thing I have not done is swap the fuel injector to another hole to see if it repeats itself.

I'm using EMS8860 engine management, MW cdi boxes, cop coils. It's wired up as sequential.

Anyone have any theories what is happening here? Not enough spring pressure, valve float?

Here is a screen shot of the data. look at cyl 3 at the crosshairs.

 

Perhaps the intake manifold design is a little favorable of that cylinder?
Sorta like #3 on B series. It supposedly runs a little hotter...
Sounds like a pretty cool setup you got there!

 

Is it allways cylinder # 3? It could be valve train, but have you tried getting the egt's around 1100? 900 is really rich... whats the head package details? does the motor sound like it's hitting a soft limiter and like cylinders are mixing....the other egt's dont do anything at 6500?

 

at 85 psi, moran's 550's are flowing approx. 750 lb/hr x 80% duty = 605 lb/hr

605 x 6 = 3630 lb/hr

3630 x 1.5 bsfc = 2,420 observed hp

bsfc could be between 1.3 and 1.8, so I went in the middle, but does that HP figure sound right? You're delivering a ton of fuel. a ton and a half per hour actually.

We've had a several sets of Moran's injectors in here; within a given set, you can have a substantial difference from injector to injector... but I'm not saying that's the culprit to your egt on #3. swapping the injector to a different hole would let us know if that's the case. or, we could always flow test them.

 

Tom and I spoke on the phone. I suspect the issue is the car is way too rich and the temps are too low. Cold intake temps, low compression, and an injector that doesn't atomize well can result in fuel going straight through the motor.

I think the dip is a misfire due to being too rich. That's my guess at least, 950deg EGT's is freaking cold! lol

I'm sure Tom will update this after they try a couple more things.

 

yeah i agree.. your too rich...
950egt is nothing..

 

Thanks for your explanation, that hp are what dreams are made of, no, it is not seeing that figure.


Yesterday we leaned it down a bit and it did the same thing, No. 3 took a dive at 6500rpm and the motor fluttered like a flag in gail force winds. EGT's went up to 1050 across the board.

There were two things that hadn't been checked, one was to move the injector to another hole to determine if the injector was at fault; two was to check that the driver wasn't wigging out. So, we put it in multipoint 720 and plugged the no. 3 injector wire into no. 2. I'm not sure if this will actually pinpoint the problem as all injectors will fire once in one complete cycle. The strange thing was the car while under boost sounded and reacted much more crisper than ever and I was able to carry the rpm's to 7000 where I elected to let off, it was still climbing and seemed it would have revved onward. HP also went up considerably. No. 2 which was no. 3 previously did not fall off like in the past.

I called it quits there as something is amiss here. I now feel like a rudderless ship on a overcast moonless night. Specialist's are requested to chime in with a beacon.

On this software there is a fuel override that adds fuel at self defined boost points. It adds fuel based on a percentage value that is created by the user. Some of the jumps may be to erratic, so my thought is to "zero" this out and build a fuel map with more resolution, such as fuel enrichment say every 2-3 pounds of boost in an effort to make it more linear, by adding rows to the map. Thoughts?


Thanks Tony (T1) for the info you shared and the ongoing customer support you've provided on the questions with the MW CDI's and the tuning education. I'll be calling on you from time to time.

 

Hey Tom,

Do you have a datalog showing injector pulsewidth? That will make it clear if it's the ecu doing something odd with the injectors intentionally.

 

Maybe the ems injector driver doesnt have enough "juice" to power that injector. Moran's from what we know take quite of bit of "juice"

 

Inj. capacity I would assume is injector duty cycle. Injector pulsewidth will give you a better idea of things because it will follow your torque curve since rpm isn't taken into account, but either way, the duty cycle shows relatively smooth so I don't think your problem is too abrupt a transition in fueling in the ecu somewhere.

No idea why the graph would show 80 and the data say 15 though. lol

 

If you look at the graph, that line extends beyond 80 at that point in the log - I was thinking it meant he had 15% duty cycle left? Meaning he's at 85% of capacity?

 

Yes, the Inj Capacity is their way of saying duty cycle. I received an email from EMS and they said "thank you, it is a software error and we'll fix it ASAP". I sent them another email asking if either one of the graphs are correct and or reliable. I'm still waiting on that one.

 

migth be an error but it makes sence if that is the actual pulswidth that is beeing displayed.


120/6761rpm = 17.75msec\cycle

17.75X0.85 = 15.09msec pulswidth

15.2/17.75 = 0.856 = 85.6% dutycycle wich is pretty much what the graph shows at 6700