SCCA CAM-C Thread

[kz]

Yeah, PSI is controlled by SCCA but is arbitrarily adjusted after RR makes his adjustments. So its definitely biased by PAX.

Exactly - arbitrarily. And in Pro it matters. I know I'm not fast enough to whine (although my only 2nd place in Pro was behind CAM-T car) but it's essential part of being an autocrosser like you said

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[LightningGT350R]

The CAM-T index should certainly be harder than CAM-C if two cars were equally prepped. "Equally prepped" would be much harder in CAM-T but difficulty of prep is irrelevant in terms of PAX.

I could imagine a Fox chassis with a level of build that should crush anything possible in CAM-C due to foot print and weight. Really no reason for that 0.020s other than only a few folks have serious builds.

CAMC get wings so the PAX is worse. Most T cars are lighter and have better power/weight, similar tire, and even suspensions are similar in some cases (IRS installed in several top T cars). There were some amazing T builds at Spring Nats this year. Motors practically in drivers seats, top notch suspensions... Just no wings. I'm confident T will take a PAX hit next year.

BTW, T cars took the top three spots at the Spring Nats Pro. Coincidence?

 

[Dallas J]

So... Theres an interesting and undesirable effect of the Ford Torque Management and BOV control on boosted mustangs when it comes to AX. When you roll into throttle and lift off throttle, the throttle body itself opens as quick as possible and stays open longer than your foot is off the throttle.

If Tq Management was able to fully pull power, like with standard bolt-ons, then it wouldnt be an issue. But with the supercharger added, we have a bunch of extra air in this small time frame where the throttle doesnt close fast enough to create a vacuum to open the BOV. The effect is a 0.1-0.2s surge in acceleration when you expect to have deceleration.

On the street, its nearly imperceptible. In fact, the F150 ecoboost does this for much longer than the mustang. In AutoX situations, imagine lifting and expecting the weight transfer and load on front tires only to push a car length past your turn-in point. Literally trashes a run.

As to the why, its for emissions to get airflow through the motor from what Ive read. And its not easy to fully defeat talking with multiple " very smart" people.

Alternate solution, make a system that stores vacuum and uses actually throttle pedal position to open the BOV based on lift rate or pedal position. So heres what Im working on to fix things.

I have a harness to plug between the throttle pedal connectors to get the signal, an arduino and relay, and some rusty programming skills I'll just burden AI with coding.

 

[mavisky]

Is this an automatic thing or does it apply to manuals as well? I grt s finish feeling in the wife's twin turbo aviator with thr 10 speed. Like if I let off from 100 to 0 its taking thay and spreading it out over half a second before it closes the throttle plate.

 

[Dallas J]

It seems to be on modern fords. Its just that boosted cars dont vent the boost right away and it causes that surge with the torque maps not accounting for that small period of more airflow than expected.

In the maps, there isnt anything to correlate pedal lift to throttle close. Its all just based on internal torque calculations. Standalones are so much easier... I need a PNP motec or haltech kit :(

 

[LightningGT350R]

I have a Vortech and would agree that the on/off throttle response (especially at part throttle) was not ideal and this may explain most of what I experienced. The car was awesome at full throttle. But any partial throttle situation was just not ideal from a response perspective. Upgrading the BOV helped but it still wasn't great. I read somewhere that using a throttle body set up to operate 180 degree out of phase works better. It doesn't rely on vacuum to open, it works directly with the existing throttle body to more accurately control boost. I'm looking for the company that sells the system but can't find it at the moment.

 

[LightningGT350R]

Found it...

 

[Dallas J]

Awesome! Im glad Im not the only one thats noticed this being a non-trivial issue.

Edit: I watched the vid and that got me thinking how to I make sure my setup isnt an on off switch with dumping. Well, I think Ive solved that before its come up.

My programming will do a few things.

1. Analog input to adjust lift rate to open valve. So you have to be lifting fast before it will dump.
2. Analog input to adjust min throttle.
3. Dump will just be a pulse of some short duration.
   1. This is needed to make sure Vac Can will recharge
   2. Goes back to engine control until the system again sees high enough throttle with a lift.
4. Otherwise the slower throttle inputs will still keep the nice throttle control at least my car has. And fast on throttle will still immediately close the BOV.

I should get off my butt and start pulling the bumper now to get to the bits..

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