CART, F1, and rev limiter like throttle
CART, F1, and rev limiter like throttle
(OP)
Do modern champ car and/or F1 engines use a throttle?
I noticed they seem to be either in full power mode, or on some some of rev limiter. Coming out of the pits, they are bouncing off a rev limiter to stay under pit speed, rather than just having less power output from a mostly closed throttle butterfly. Also, they don't seem to idle steady either, seems like a rev limiter is used to keep idle speed.
Also lack of any blow off valve (never heard any anyway) on the champ car turbo engines leads me to think maybe they don't have a throttle.
Is this perhaps a suitable way to run throttleless, on a drag strip car? Obviously not very feasible for driving to work.
The idea is like this. Fuel injection events are set to full or slightly leaner than stoich. Throttle input (electronic), would incrementally control a soft fuel rev limiter. At 0% throttle, 60-70% of the fuel injection "squits" would be skipped, keeping the engine at a idle speed. As you increase throttle input, the % of skipped squirts would go down, increasing power output. By 100% throttle, there would be no skipped squirts.
Would operating a engine this way damage it from the unbalanced operation? Or would it be ok as the skipped squirts will move around between cylinders constantly?
I noticed they seem to be either in full power mode, or on some some of rev limiter. Coming out of the pits, they are bouncing off a rev limiter to stay under pit speed, rather than just having less power output from a mostly closed throttle butterfly. Also, they don't seem to idle steady either, seems like a rev limiter is used to keep idle speed.
Also lack of any blow off valve (never heard any anyway) on the champ car turbo engines leads me to think maybe they don't have a throttle.
Is this perhaps a suitable way to run throttleless, on a drag strip car? Obviously not very feasible for driving to work.
The idea is like this. Fuel injection events are set to full or slightly leaner than stoich. Throttle input (electronic), would incrementally control a soft fuel rev limiter. At 0% throttle, 60-70% of the fuel injection "squits" would be skipped, keeping the engine at a idle speed. As you increase throttle input, the % of skipped squirts would go down, increasing power output. By 100% throttle, there would be no skipped squirts.
Would operating a engine this way damage it from the unbalanced operation? Or would it be ok as the skipped squirts will move around between cylinders constantly?





RE: CART, F1, and rev limiter like throttle
When these overspeeded a link is pulled out of the injector drive, so the engine gets no fuel for that cycle.
At a rough guess you'll only be firing about once in every 4 or 10 opportunities, ah except that you will be pumping a lot of air, that might put the load up.
Very interesting idea.
Cheers
Greg Locock
RE: CART, F1, and rev limiter like throttle
I just watched F1 qualifying, and paid close attention to the engine note as they entered the corners and backed off the throttle. The engine note changed a lot, getting "rougher," indicating a "hit and miss" load control. Not to be confused with the rough note of traction control, which is rougher still, when they are coming out of the corners.
RE: CART, F1, and rev limiter like throttle
RE: CART, F1, and rev limiter like throttle
I have no data nor real feel for the numbers here, but intuition tells me is is quite low in the overall scheme of things.
I am at a bit of a loss as to why throttle-less speed control is seen as an advantage here, as there are no losses at WOT (at least with slide throttles), and part throttle is a deliberate loss in efficiency, so why worry about the loss in efficiency then, unless chasing fuel economy. The part throttle fuel economy savings in an application where most time is spent at WOT would be very small, but I guess cuts a little weight from the car with a full fuel load aboard, and reduces refuelling time by maybe less than 0.10 sec or something like that.
I guess there is a slight weight saving in the manifold and a slight cost saving re investment and maintenance, once the original software is developed.
I expect, as to whether or not I just contradicted myself lies in the detailed analysis of some very marginal numbers.
Thats my 2 cents worth, and I guess it's a two way bet.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
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RE: CART, F1, and rev limiter like throttle
Your emission control will be stuffed as you'll have too much oxygen in the exhaust, so only do this in open loop.
Cheers
Greg Locock
RE: CART, F1, and rev limiter like throttle
For race cars with individual air stacks for each cylinder (most hi-po NA motors), this would remove the need for 6-12 little throttle bodies, and all the flow balancing needed as well. This would make individual stacks cheap and easy, instead of complex and expensive. The flow increase without the butterfly in the center would be a couple % I'd think.
Would run cooler, as more air is being pulled through the motor acting as a internal radiator.
You wouldn't need any form of idle control motor. On a turbo car, the BOV wouldn't be needed anymore.
I figured out the frequency of skipped pulses in average use, and it would be enough (cruise would probably drop out 40-60 pulses a second) that it wouldn't cause a uncomfortable vibration. The engine note would just be funny.
I do realize this would make any cat converter stop working, but it's not intended for cars with converters anyway. It would probably "cheat" through a emissions test, with all the extra air to dilute the exhaust gasses.
RE: CART, F1, and rev limiter like throttle
If you have access to program your ECU for speed control like performance to control staging, I guess the ECU can handle start and idle at no throttle, staging at first click, then hand over to traction control at second click.
Is traction control legal in the class you intend to run.
This would also reduce the load on the rods, rod bolts and pins on lift off at high rpm, thereby allowing either slightly higher red line or slightly lighter components in the reciprocating parts and crank.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: CART, F1, and rev limiter like throttle
I didn't think about the throttling strain on lifting at high RPM. Good point. Throw another thing in the positives column.
I don't plan to run any class at this point. Just gonna go for ET bragging rights, and get noticed for doing things a little different. The car will certainly have a distinctive tone if I used this method.
Gonna ask one last time, anyone think there is some inhenently bad thing in concern of wear about running it in this high speed "hit and miss" style?