Are 2-step rev limiters allowed?

Guest · Post by **Guest** » Mon May 16, 2005 2:22 pm

A 2-step rev limiter used on a turbocharged car has the ability to make boost while stopped (i.e. before you leave the starting line).

The 2-step cuts fuel and/or spark in order to mimmick a load on the engine that gets the turbo spooling. A side afffect of this is a back-fire-type noise for a few seconds prior to letting the clutch out.

We finally got the 2-step working 100% correctly in my car this weekend at the NHRA Sport Compact event at Atco. Video here:
http://www.jekylhyderacing.com/images/h ... epping.mpg

Is there any reason I can't use this at the start of a hill climb? I don't imagine that it would be an issue, but I did not want to scare anyone if they hear the popping of the 2-step at the starting line.

Thanks for your time and input.

JekylandHyde · Post by **JekylandHyde** » Mon May 16, 2005 2:23 pm

^^ that was my question ... wasn't logged in a gain ...grrrr ...

Post by **Matt Rowe** » Mon May 16, 2005 9:39 pm

You know I usually try to found out what is wrong with my car when it sounds like that.

I assume you are still running STMOD which means engine control systems are unrestricted so the system is certainly allowed. Currently we have no sound level restrictions so there would be no problem there. And besides we let those SAABs run so why would we stop you. I'll have to check and see what some of the other officials think but I don't see a problem.

Tim Royer · Post by **Tim Royer** » Mon May 16, 2005 10:30 pm

HI,

Looks like your going to be doing alot of smokey burnouts at the startline. Your adding more HP on your launch, I don't think that the tires will hold for you DOT stickys any. Drag slicks on a hot tire would. I think you'll see to much engine and no traction = slower.

But it will be cool!

My 2 cents

JekylandHyde · Post by **JekylandHyde** » Tue May 17, 2005 6:27 am

Matt, thanks for the information. I just want to make sure I am playing fair. As for how it sounds, yes it sounds like the thing is going to explode ... and it does, right off the line

Tim, last year I was racing on actual street tires (225/17 Falkens) with 320 rwhp or so. This year I am on 265 Kumho V700s and I put down 380 rwhp.

I can share another video of my launch from this weekend on 275 BFG drag radials (also a DOT tire) ... almost pulled the front wheels up. Granted I could do a burnout and run 16 psi of tire pressure at the strip.

... but a really good clutch slip = control on traction

I hope.

Steve Tumolo · Post by **Steve Tumolo** » Tue May 17, 2005 8:23 am

All I can say is that I hope you have either a scattershield or a blow proof bell housing. After a certain amount of hits like that to the driveline something is going to give. IMO anything you gain buy doing a launch like that will be lost somewhere on the hill.

Guest · Post by **Guest** » Tue May 17, 2005 8:29 am

Yes, I have a scatter shield Steve.

Most MR2s that make 300+ tend to explode CV joints, but I have those upgraded as well. For what it's worth, when I go drag racing, I do my burnouts by dumping my clutch at 6500 rpms @ 20 psi of boost in 2nd gear with only 14 psi of tire pressure in a 275 wide tire. That's a bit of a shock to the drivetrain and seems to hold up.

Here are some more videos if you guys are interested:

This was my burnout in the 1st round of eliminations this weekend.
http://www.jekylhyderacing.com/images/h ... urnout.mpg

Hyde's wheels do not come off the ground (I watched closely on the big TV), but notice the suspension stays unloaded for all of 1st gear. If we resolve our 2nd gear boost issues, we can keep that squat rolling down the track:
http://www.jekylhyderacing.com/images/h ... street.mpg

JekylandHyde · Post by **JekylandHyde** » Tue May 17, 2005 8:30 am

grrr .... this is the only message board I am on that let's me post without being signed in. *scratches head*

Tim Royer · Post by **Tim Royer** » Tue May 17, 2005 12:23 pm

Delete the cookie for pahillclimb.org in cookies folder. Then resign in and click allways keep signed in or whatever it says in log in screen. Should fix that for you.

Guest · Post by **Guest** » Tue May 17, 2005 12:25 pm

Is this just a typical turbo anti-lag system?

If that's what it is, it not only helps with starts, but also keeps the turbo spooled during gear shifts and braking zones. Your car will be faster up a hill, regardless of what tires you use.

The only downside is turbo and cat life, but those can be replaced/rebuilt....

JekylandHyde · Post by **JekylandHyde** » Tue May 17, 2005 12:38 pm

Anti-lag is different than a 2-step rev limiter.
A 2-step revver is only used for the building boost before you launch.
They are primarily used for drag racing, but in a standing start road course they can be advantageous.

I am not interested in anti-lag because of the harm to the exhaust manifold and turbine (I have no cats or kittens to worry about

).

JekylandHyde · Post by **JekylandHyde** » Tue May 17, 2005 12:40 pm

I'm actuall going to need to install a toggle switch on the dash to turn off the 2-step after the launch so that it does not kick in going up the hill.
It could actually cost me time as it could pull revs down on shifts with braking/slowing.

Tim Royer · Post by **Tim Royer** » Tue May 17, 2005 9:56 pm

Hi,

Connect it to the clutch pedal, use a safety clutch switch

JekylandHyde · Post by **JekylandHyde** » Wed May 18, 2005 8:14 am

The clutch pedal switch is what switches it from the low rev limit to to red line.

When I am ready to launch (clutch in), the lower rev is set so I can build boost. When I release the clutch it goes to the higher (Redline) limit.

Anytime I put the clutch in, it would want to enact the lower limit though.

Tim Royer · Post by **Tim Royer** » Wed May 18, 2005 12:42 pm

HI,

This should be easy. Take the wire that gets hot when the switch is engaged and run it to a new switch that you can mount so it will only engage when it in first gear. You should have room down by the shifter to make up a mount for the switch. You would only need a 2 wired switch at about 10-20 amps that the hot wire would run through to complete the ciruit. This way it would only engage your low rev with clutch and in first. That would be the best solution I think.

JekylandHyde · Post by **JekylandHyde** » Wed May 18, 2005 12:53 pm

I like your thinking Tim, but I must confess that I am a fool with electrical things.

Also, I use the lower rev limit in 2nd gear as well for doing my burnouts (2nd offers more wheels speed = better burnout).

Tim Royer · Post by **Tim Royer** » Thu May 19, 2005 12:56 pm