WR58

I am currently building a S2000 powered autograss racer. It will be mid engined, using a hewland / vw tranporter gearbox.

The exhaust will be a custom made job to suit the car, the inlet currently been made by Jenvey (8 injector system, n/a). The ecu is causing me a few problems. At the minute, top of the list is the P8Pro system from DTA (www.dtafast.co.uk). THe system will run the injectors, over plug coils & vtec. Its a question of when / how to vtec. The system will not emulate the Honda unit & vtec will need a dedicated switching point. Various outputs could be used, RPM, undriven wheel speed, air temp, water temp etc.

My idea is to vtec above a preset wheel speed - the train of thought being running round the pits etc. would be on normal non-vtec. On the startline, the rev's would be high (say 6000 - 7000 rpm) when I drop the clutch - Because the wheels are not turning this would mean the unit would over fuel. The plan is that the ecu would reconize this through the wide band lambda sensor & reduce the fueling.

When the clutch is released, the engine will still be on non-vtec timing. My best guess is that the less power will be put through the gearbox limiting wheel spin, giving a better get away.

Above a preset wheel speed, lets say 20mph the vtec will be activated putting the full power down, for the duration of the race.

The knock sensor will not be used.

Rules within the sport mean that traction control is not allowed.

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The second option would be to go with the more expensive Motec system which runs the vtec.

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Third option (the one that is been used by someone else) is to use a solid pin. Therefore the vtec is alway active - much easier to sort the timing out.

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So, does anyone see any problems with my plan? Is it feasable or am I talking rubish? Any advise much appreciated.

jimknapp

If you are going roundy round racing you should DEFINITELY wire it up as automatic as you can. I run the world's fastest S2K and currently just turn it on with a toggle switch part way through first gear. But we only do straight line stuff and I only have to turn it on once.

As to trying to run VTEC with a pin, i.e., all the time, it's not really feasible. I 've done dyno pulls with my car with VTEC on from 2000 rpm and it just beats the daylights out of the car. It really needs to rev to 3800 to 4000 before it becomes usable. Below that it just REALLY slows you down. And good luck timing the motor although I suppose you could just run it to 5000 and go for 34 total.

And a lambda, even a wide band can only do so much for you. You have to be basically in good tune without the lamda and then use it to do small adjustments, probably not more than one full number either way on the mixture ratio.

BTW I run an Electromotive Tec III.

Turtle

Talk to Richard @ Blink Motorsport. Helpful chap, who put an F20C into a Westfield a few years back, using a DTAFast Ecu. Used the rev limiter to activate Vtec at the right rpm, which is a good way of doing it.

HTH

-Brian.

hans

I've put an unmodified F20C (S2000) engine in my Westfield using an ECU from AEM. I think it's derived from a GEM/Emerald unit.

For switching into VTEC the ECU takes the AND of four adjustable thresholds: car speed, engine speed, throttle position, and engine load. To drop out of VTEC the ECU takes the OR of other thresholds on the same parameters. The ECU adds a defined (and fixed) fueling and ignition advance when in VTEC. All 10 parameters are user-settable, so, of course, they can be set to have no influence.

I use an AND of 0 mph, 5500 rpm, 60% throttle, and -4 psig manifold pressure to trigger VTEC. I drop out at 5000 rpm, independent of other values. Since my maps reflect this, I add zero fuel and timing with VTEC.

The AEM ECU also allows engine-acceleration-control that's FULLY defined by the user. (I didn't call it traction control; some might.) It requires no sensors other than the stock Vehicle Speed Sensor (VSS) that drives the speedometer. "It's only software."

I'm happy with my ECU, though FULL programmability is certainly a challenge.

WR58

Hans,

Thanks for that - interesting post. I will look into the AEM ECU - the DTA is a nice unit, however all these systems do the same thing, the DTA software is incredibally user friendly (I have previously used one on a VX XE installation).

What inlet did you use?

What was power outputs did you achieve?