Adapt aftermarket TPS to stock ECU

[Jon_UBCO]

My team is in the midst of the build on our first FSAE car, and we've hit a bit of a snag.

We're planning on using an Active-Technologies FSAE 28mm throttle body with our Yamaha Genesis 80FI engine.

Link to TB (http://atpowershop.co.uk/catalog/formula-student-28mm-single-bore-throttle-body-p-101.html?osCsid=028c64f2c7d37fcc2d21a5d94dad014e)

We don't have any tuning facilities (aside from a wideband 02 sensor), so we're planning on using the stock ECU with a simple fuel-compensating piggyback unit.

This is the problem: I've been told by A-T that the aftermarket throttle body is mounted with a TPS that ranges from 0-1200 ohms, where-as the stock TPS ranges from 0-6000.

Is there any way we can modify the input system so that the ECU doesn't think we're at 20% throttle with when in fact we're at WOT? Or is anyone familiar with these throttle bodies, and perhaps knows of an aftermarket TPS that will fit and read properly?

Thanks

[Jon_UBCO]

My team is in the midst of the build on our first FSAE car, and we've hit a bit of a snag.

We're planning on using an Active-Technologies FSAE 28mm throttle body with our Yamaha Genesis 80FI engine.

Link to TB (http://atpowershop.co.uk/catalog/formula-student-28mm-single-bore-throttle-body-p-101.html?osCsid=028c64f2c7d37fcc2d21a5d94dad014e)

We don't have any tuning facilities (aside from a wideband 02 sensor), so we're planning on using the stock ECU with a simple fuel-compensating piggyback unit.

This is the problem: I've been told by A-T that the aftermarket throttle body is mounted with a TPS that ranges from 0-1200 ohms, where-as the stock TPS ranges from 0-6000.

Is there any way we can modify the input system so that the ECU doesn't think we're at 20% throttle with when in fact we're at WOT? Or is anyone familiar with these throttle bodies, and perhaps knows of an aftermarket TPS that will fit and read properly?

Thanks

[Jon_UBCO]

In addition, A-T sells these throttle bodies with a Wabash TPS which ranges from 0-5000 ohms.

By my logic, although if we used this TPS the ECU would think we we're only at 80% throttle when at WOT, the reduced airflow through the intake restrictor may make this lower throttle setting beneficial rather than detrimental.

Thoughts?

[Jon Burford]

We too are using a genesis 80 fi engine this year! what university are you at?
Off the top of my head I cannot think what the standard genesis TPS looks like but could you make a mechanism by which it attaches to the AT throttle body?
With regards to using the original ECU, I'm not sure it would be the best choice.
You would need to tune in the throttle body for sure but also the genesis uses twin MAP sensors for fuel compensation (one in each inlet runner). I'm not sure how well it would work without reasonable readings from these.
Feel free to prove me wrong!
Let me know how you get on!

[Adambomb]

+1 for not using the stock computer, these days you can get a Megasquirt cheap enough that I really can't imagine any advantage at all to trying to piggyback a stock system.

Although, if you were desperate enough, if you just want the electronics to play nice you could throw together an op-amp to manipulate the voltage to what you need.

[Jon Burford]

yeah try and get programmable.
I strongly recommend a DTA Fast unit.
They are really good for value for money, excellent performance and the support is fantastic.
Also we are running our genesis 80 with a DTA so if you went that way I'm sure we could lend and hand getting the crank and cam stuff all setup. just spent a good week getting it spot on.
Obviously if you don't have any tuning facilities you have a problem. Do you know anywhere local that might have? a rolling road is better than nothing a Dyno is obviously favourable.
Let us know if you need any more help

Here's the link to DTA Fast
http://www.dtafast.co.uk/

[Jon_UBCO]

This is my first year as project manager and team lead, I only saw the car a couple times last year. I've been blessed with the responsibility of making this car drive, that's about our only goal.

The crew before mine actually did spent a large lump of sponsor money on a Microsquirt system, and they absolutely destroyed is. As have they destroyed two stock Phazer wiring harnesses.

At this point, we have very little choice but to make this car work with the stock ECU, supplemented by the Attitude Industries compensator.

Link to piggyback unit (http://www.tunewithattitude.com/products.php?pr=47&PHPSESSID=12fd289b1bf2ee789d6238e04c9e541a)

The university is losing faith in the project as they've seen relatively little progress over the past couple years. If we can't get this car driving with these components, I don't think FSAE will have much of a future at the university.

Additionally, we have no available dyno for tuning, so even if we did go with an aftermarket ECU, we couldn't map it properly.

[TMichaels]

Why do you not just mechanically attach the stock TPS to the throttle body?
May not be the most elegant solution, but it sure is the easiest.

Regards,

Tobias

[Jon_UBCO]

I haven't ruled out that possibility yet, but I'm not sure what kind of shaft the new throttle body will use. Our stock TPS uses only one mounting hole, whereas all of the versions they offer use two.

[TMichaels]

Well, building a mechanical adaptor should be the easy part.

Regards,

Tobias

[Mumpitz]

Does it really matter what the resistance is? If the TPS is just acting as a voltage divider it may not matter what the resistance is as long as the signal voltage is linear 0-5V from Idle to WOT. I'd check the stock one with a multimeter and see what the voltage output from Idle to WOT is first. That being said it is possible that there is more internal circuitry that would prevent any ole TPS from working. Worth some investigating though.

[Jon Burford]

Yeah sounds like a mechanical adapter would be easier, the shaft from the AT throttle is rectangular. have you ordered it yet?
The tricky bit will come when you mount the tps on the new body, it will need to be in exactly the same configuration as on the snowmobile. I.e. at 0 at the same point and wide open at the same point. Closed throttle is seldom when the tps lands naturally, it is offset. Not impossible to do, but it will need to be done accurately for it to stand a chance. I was thinking about the twin MAP sensors, It would probably be ok to put one in each inlet runner from your plenum. I would imagine that's as close as your going to get to what it expects!

[RollingCamel]

Check the rotation direction, we ran into this issue.

[Brian Barnhill]

Talk to A-T if you really want to use the stock TPS with their TB. They built one for WPI back in 09 (when the team first tried using the Genesis 80FI engine, but never finished the rest of the car that year) When the engine made it to competition in a car last year it was on a Haltech P2000.

That said, I also would suggest against the OEM ecu/piggy back.The engine dynamics change drastically on this engine with the restrictor and exhaust changes (think about that carefully and that the engine is odd fire when designing these components.) Until you can get those components working right and the CVT dialed in the tuning can really be a bear. With the Haltech and just a little math it was pretty simple to get a solid base tune though.

[Jon_UBCO]

We haven't ordered it yet, we're waiting on repairing the harness and checking to make sure the engine runs properly in a stock configuration before modifying it.

Thanks for all of the advice, I'll get back in touch with A-T and see what they have to say.

[theloyal]

we are a rookie team and we also using AT power Throttle body and restrictor assembly on our Honda CBR600RR engine, we purchased the penny and giles TPS that is on the site of AT power, but it didnt function with the stock ecu.

therefore we are using the stock TPS now, its actually bigger than that penny and giles TPS, so we created a flange using a SS sheet (3mm) and used the the AT power holes for penny and giles TPS mounting to fix that flange on it, and drilled two holes on that flange where we could fix the stock TPS.

its functioning properly now!