Limited-power mode?

[dalves]

I'm in the early stages of planning out a build, still looking at all the options for parts. I've been looking at a BluePrint 347 with EFI or a Coyote gen 3, which are both 400+ HP. I was thinking it would be great to have the option of traction control for safety, as well as a limited-power mode so that I can let a friend drive it, teach my kids to drive stick, etc. with less risk of getting into trouble. I'm not sure the best way to limit power: timing? shutting off cylinders? rev limiting? I'm also not sure which option (347 vs. Coyote) would be better for making my own limited-power mode.

Coyote: I've heard that MoTeC is a good option recommended aftermarket ECU that supports traction control and many other features. The throttle is "drive by wire" so it seems like it should be possible to have the ECU limit RPM by just adjusting / limiting the input. I guess my concern is that everything seems very locked down so that only professional approved tuners can modify their system, so it might be hard to tinker with and/or expensive.

BluePrint 347 + EFI: I think the throttle is a physical linkage so I'm not sure if there's a way to limit revs -- is it easy to retrofit a drive-by-wire throttle body? Or maybe I should just be looking at disabling cylinders / adjusting timing? It seems Holley has a ton of EFI systems that are well-regarded, but I'm not sure which ones would be a good choice for what I want, and how that compares to the Coyote option.

Apologies if any of the questions here don't make sense, I'm very new to all this :) Excited to learn though!

Thanks,
David

[Jim1855]

Put a brick under the gas pedal. Well, that's the basic concept.

I'm working on a design to limit the gas pedal stroke to do the same thing and allow new track drivers to learn in the car without full power. I believe that it would be best to restrict pedal movement rather than restricting carb or throttle body opening due to the length and connections in the linkage. Should be less chances to bend something.

Throttle blade opening is what controls torque and for most engines torque is all in at 4k RPM of you have full opening. Just restricting RPM will not stop full on torque and the associated wheelspin.

Good luck.

Jim

[Jeff Kleiner]

Rev limiter or throttle stop isn't going to do it...you can get in plenty of trouble below 3,000 RPM. Not intending to be a wise guy but the best solution is to make sure that there's a good connection between the brain and right foot. If you're not confident that your friend/kid/whatever has that don't put them behind the wheel.

Jeff

[DW66]

I'm on the same page as Jeff.

Dave

[kirby]

I don't necessarily disagree with any of the comments here but do have to wonder if it is possible.

My build is in process so I am not to this point yet but have thought of the same thing for my kids, wife, etc.

Automakers have done it for years with valet keys, dodge pulls it off in their demons, turbo cars go into Limp mode. Surely it is possible and if someone finds out how to do this on a gen 2 coyote I may copy it. In fact when mine is in for tuning I am going to ask the same question. I agree that RPM is probably not he right answer but pulling timing may be.

[weendoggy]

It can be done with aftermarket systems. I know I can do that with my Holley HP. You just detune the engine and load the tune. Basically you make it fall flat on its face. However, I respect learning correctly as Jeff says. Why punish the engine when it's the operator that's controlling it. jmo

[edwardb]

X3 what Jeff said. It's all theory until you actually drive it IMO. I was scared of my first build (now a number of years ago) and was pleasantly surprised that it wasn't hard to drive and actually well mannered. You might be too. If you mash the throttle on any car, including daily drivers, trouble can be the result. I've let both of my sons drive my cars (adults, good drivers) but that's it. Others have asked, and I offer them the passenger seat.

[Lidodrip]

With regards to kids driving - you may find it hard to find an insurance company that will insure kids driving a Cobra. My teenage boys spent two years building our car and it was disappointing to discover that they could not drive it after we finished it. I spoke with Robin at Midwest Classics who is very knowledgeable about insuring Cobras and he said that he was unaware of any companies that would insure someone without 10 years of driving experience. The company my insurance agent ended up using (American Collectors) said they would consider insuring my kids when they had 5 years of experience. For my oldest, that is 8 months away and he is counting down the days...

I completely agree with Paul and Jeff that the most important limiter is the neural connection between the brain and right foot. I too was pleasantly surprised about how well mannered the car was to drive. I only have experience with the Coyote engine, but it has been great in all respects.

James

[bobl]

As Weendoggie said the Holley ECU (probably others too) will do everything you are wanting. I also built traction control in mine by adding speed sensors front and rear. But even with all that nothing makes up for poor decisions.

[john42]

With regards to kids driving - you may find it hard to find an insurance company that will insure kids driving a Cobra. My teenage boys spent two years building our car and it was disappointing to discover that they could not drive it after we finished it. I spoke with Robin at Midwest Classics who is very knowledgeable about insuring Cobras and he said that he was unaware of any companies that would insure someone without 10 years of driving experience. The company my insurance agent ended up using (American Collectors) said they would consider insuring my kids when they had 5 years of experience. For my oldest, that is 8 months away and he is counting down the days...

I completely agree with Paul and Jeff that the most important limiter is the neural connection between the brain and right foot. I too was pleasantly surprised about how well mannered the car was to drive. I only have experience with the Coyote engine, but it has been great in all respects.

James

Hagerty actively advertises building/restoring a classic muscle car with your teenage kids. If you call them to get insurance for said kid, it's a flat "No". I don't know why people like Hagerty so much. They are far more expensive then any other option I could find and seem to be rampant with bait and switch rules.

[Erik W. Treves]

While I completely agree with everything above - people can hurt themselves in much lower horsepower cars (they do that all the time) and there is no replacement for good grey matter between the ears..... if you go drive by wire, might take a look at a "pedal commander" - the one I have used (will be using) is the evcX Throttle Controller - it has a valet mode that only allow 50% throttle - it has a bunch of other features - You can still kill yourself at 50% throttle - but it's something to consider.


https://www.youtube.com/watch?v=zXWRygcBW6Y

[John Ibele]

I'm sure you'll continue getting all sorts of ideas for things to install to limit engine performance in certain conditions. I asked myself two questions when I was pondering this during my build. Would any of those add-ons leave me feeling confident about keeping the car wreck-free if I didn't trust the skills and judgement of the person behind the wheel? And if I didn't trust the person behind the wheel, would I hand them the keys?

As Paul mentioned, I too was apprehensive before driving my build, and I focused on drivability with every major decision. I couldn't be happier with the manners of my car as long as my right foot minds its manners as well. The biggest contributors in my mind: a throttle that uses full pedal travel and has linear, smooth response. A cam choice that gives decent low-RPM performance. Brakes that stop the car well. A clutch that you can get used to. And (power) steering that is responsive but not twitchy.

The biggest risk to your car is handing over the keys to the wrong person. No doubt you've got a handle on this. Knock yourself out on all the engine / traction control options, sounds like fun. But definitely pay attention to the drivability of the car, both for your own enjoyment and the enjoyment and safety of any other potential drivers. Good luck and have fun!