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FC FI ITS built car, odd behavior 6600 rpm + dyno charts
Let's make this efficient.
1986 shell
S5 motor
Built and prepped in early 2000s was very successful in ITS club racing. It was parked in 2005 and we brought it back to life this spring/summer. We cleaned the tank, replaced fuel lines, replaced fuel pump with unit from 2006 Evo IX, had fuel injectors cleaned professionally (Diesels Bow, NH), rebuilt fuel pressure regulator, replaced circuit opening relay.
Car starts And runs well! Today we put it on the dyno!
And here are the charts (I promise to get better pictures)
Absolutely love this trailer!
Now for red flags: low hp, running lean (pressure set at 50 will drop to 43 ASAP) car stumbles above 6600. Car does not have a timing gauge.
I believe this is a combination faulty ignition and fuel pressure too high.
Current ignition: stock coils, rb plug wires, (new) spark plugs.
I hope I have provided enough information to stir some insight from this excellent community.
You need more fuel pressure, not less...motor is lean...add fule. What engine control unit are you running?
Stock ECU(case says speedsource), Fuel pressure was set at 50 psi during dyno pulls. also po did not have manifold hooked up to FPR. could that cause a lean condition?
SpeedSource put Motec 4 ECUs in stock boxes back in the day. You need to open the box to see what you have. If you have a Motec, contact Steve Eckerich for tuning. You are 40hp off.
You need more fuel pressure, not less...motor is lean...add fule. What engine control unit are you running?
As I understand fluid dynamics (in fuel related units)lbs/hr decreases as psi increases. This is confirmed by examining fuel pump flow charts published by manufacturers. Also confirmed with a stopwatch hose and measuring cup ;-).
Fluid dynamics, yes. But this is automotive. I have about 500 pulls on a dyno and I always add pressure (since we are using a given diameter orifice) when we need a richer the mixture. However, you want the correct pressure at the injector for the best gas cone. Generally that is 45ish psi and adjust the injector dwell accordingly.
Considering, why then whilst running 50 psi a higher output pump and (assuming) failing coils are my Afr's above 13 consistently? I don't know a cart about comp tuning, I see why Dave uses a carb! I would think the failing coils would cause less fuel to burn decreasing my Afr's.
I'm running mostly on observation, my engineering education and a bit of unrtested hypothesis about failing components. I appreciate everyone's insight keep it coming!.
As I understand fluid dynamics (in fuel related units)lbs/hr decreases as psi increases. This is confirmed by examining fuel pump flow charts published by manufacturers. Also confirmed with a stopwatch hose and measuring cup ;-).
more fuel pressure = richer. the injectors are open a static amount of time, if you have more pressure behind them more fuel is going to go through them in that time.
the pump is different, it has the pressure working against it (on the output side) opposed to with it (on the input) the higher the pressure the more the pump has to work against.
I agree you need to open up the ECU. if it has a speedsource sticker on it, I would assume they've messed with it. you should look to see how. whether it's just a chip or an entirely different ECU inside. the ECU might be programed to run different injectors or non-stock fuel pressure.
I opened the ecu and confirmed it is a modified stock ecu. The PO said the car had no rev limiter. We had to swap in a spare pump hanging around, it came out of a Mitsubishi EvoIX so there is a flow increase there. Thank you for helping me understand that Eage. As I said in OP fuel tank has been restored fuel lines replaced fuel filter replaced injectors clean and bigger pump should equal rich?!?!?!?!
Can testing of the coils be done without the SST mentioned in the FSM?
For those experienced dyno guys and tuning forks! because of the turn at the end of my exhaust the sensor was in the immediate exhaust stream. This is significant, I think, because Mike at Kinetic, pointed out that it should be operating in clean air and was not despite the long copper tube he used to extract exhaust gases. In my first Dyno run my AFR's were in the 15's AHHHHH, thats scary! Can this measurement be considered accurate given circumstances?
Fuel filters, fuel filters, fuel filters (includes fuel pickup's in tank). Even if they look great, either take them out for testing or replace them with new. I won't get into the storys, but on rotarys this has burned me multiple times now, and never ever ever makes sense. My 2c, good luck!
OT- Where in NH are you? Heading to NHMS for track days any time soon?
Thanks for you 2c ;-). I will consider but the current fuel filter has about 2 hours of run time through it. I will look again at the pump sock. As I stated in op most of fuel system is new or restored. I'm seriously considering if my lean readings were a matter of the way wideband was setup. And frankly my Afr's are the least of my concern right now. I need to figure out why it's breaking up above 6.6k. I don't think the breakup is fuel related.
Today i disconnected the Trailing coil and the car ran and idled relatively smoothly. We also grounded each coil output individually and noticed the trailing side seemed much weaker and slower. also when we hold the car at any rpm it seems to break up. This furthers my suspicion about coil failure can anyone confirm or deny this?
I can post a video if that helps.
It sounds like fuel or spark, I would consider swapping the fuel pump to a more commonly used fuel pump?(I could be off base because I'm not well-versed in the Evo pumps capabilities) As well as consider sending the ECU off to be tested for the modifications done.(and it's working properly) I have a few sets of stock coils if you want/need to borrow or purchase for comparative testing let me know
GL Rikk
07-21-15, 06:20 PM
