Trap speed question

[9T1 Red ZR1]

What trap speed would you expect from a completely stock 1991 ZR-1 in a 1400 foot roll race with a 55 mph starting speed?

Thanks,
Bill

[Bob Eyres]

My guess is about 130 mph.

Real racers go from a dig. A stock 91' will do 107-110 from a standing start in the 1/4 mi. which is 80ft. shorter than your race.

There are too many variables to accurately predict. So, did you try it?

[9T1 Red ZR1]

Hi,
I did try it, my speed ranged from 115 to 118 on 5 runs. I didn't miss any shifts or anything like that. The car felt strong in first and second, third felt OK, but I don't know since I never run that fast on the street. I thought it was a little slow. I have new injectors, plugs, coils and wires installed. I will have to check my fuel pressure. I can't test it now, my alternator went out as I was 1 mile from my house on the way home. Thanks for your response.
Bill

[JFFerner]

Did you really try to accelerate from a 55 mph starting speed in first gear?

[9T1 Red ZR1]

No, there was a 240 foot run up to the start line. For the run to count, you had to be at 55 mph plus or minus 5 mph. I was in second at the start line when I opened it up wide open. It was a little tricky not going too fast at the start, but I wasn't real happy with my speed at the end. I'm not sure if I was losing power. When I turn my key on, the vacuum pump only runs for a few seconds, then stays off for about 45 seconds so I think my secondaries were working OK. I was just shifting into 4th by the end, shifting at an indicated 7000 rpm.

[vilant]

I've read before about power loss due to heat soak from the engine. That's why some have they're air temp sensor moved off the air horn and have the radiator fans come on at lower temps. Is your tach calibrated? You can check through the AC display.

[9T1 Red ZR1]

Those are good suggestions, I will look into that. Thanks, Joe.

Bill

[vilant]

No problem. Forgot to mention, if you still have the original accordion between the filter and air horn and you don't have Marc's rings in there, the accordion could be collapsing under load and restricting air flow. Get the rings or a Samco duct, depending if you like the original look or not. I have the rings.:cheers:

[9T1 Red ZR1]

Joe, It's funny that you mentioned those rings. I was on Marc's site and saw them as well as a new chip that has calibration to deal with engine heat. Very good advice.

Thanks,
Bill

[Bob Eyres]

What was the ambient temp when you were running? I wouldn't think you'd have much of a heat problem in Pa. at this time of year.

[9T1 Red ZR1]

It was in the 70's but you had to sit in line waiting for 10 to 15 minutes between runs. I shut the car off but I probably should have opened the hood to let some heat out.

Thanks,
Bill

[9T1 Red ZR1]

It was a strange situation. It rained that morning, so they had all of the drivers drive up and down the track at around 30 mph for about 20 to 30 minutes to dry the track off. The car was at full operating temperature when the racing began.

[Paul Workman]

Seems a little slow to me as well; perhaps partially for reasons mentioned. It is hard to relate to the unusual race criteria, but for sure you shouldn't be shifting into 4th at 115 or 118 mph with a stock 3.45 differential. If, as you say, you are shifting into 4th, then you're short-shifting by a bunch! I'd suggest you run it out in 3rd, AND consider installing a shift light (far more accurate and you don't take you eyes off the road/track).

From Mark Haibeck's web pages:

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/ZF6MPH345vs410gearratio-Haibeck_zps837f03ef.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/ZF6MPH345vs410gearratio-Haibeck_zps837f03ef.jpg.html)

For a rough comparison, my stock best run from a dig in the quarter mile (1320 feet) trapped at 113mph. So, with an extra 80 feet, AND a 55 mph roll-on, well...yeah: I'd agree that something isn't right. But, let me be clear: Is the 1400 feet including the roll-on distance, or is it 1400 feet after the 55 mph mark?

In short, Heat, tach calibration, and the snorkel collapsing are all things I've experienced having a negative effect on trap speeds.

[9T1 Red ZR1]

You are correct, the 1400 feet is the length of the race after the start. Is there a link to connecting a shift light? I've never checked the tach calibration, but as you say, it would be nice to not have to look at it.

Thanks,
Bill

[Paul Workman]

You are correct, the 1400 feet is the length of the race after the start. Is there a link to connecting a shift light? I've never checked the tach calibration, but as you say, it would be nice to not have to look at it.

Thanks,
Bill

Here's a link (http://www.zr1.net/forum/showthread.php?t=19311&highlight=Raptor+shift+light) to a thread on shift lights. Personally, I like the mini-Raptor light that can be hidden behind the AC grill. It is out of site except when it is lit. Then there is NO trouble seeing it, even w/o taking you eyes off the road.

Do you have an FSM?

[9T1 Red ZR1]

Thanks for the link. I do have the FSM. That is a great idea to install the light there. Thanks for your help, that is why this site is the best!

Bill

[A26B]

This may help.
http://i190.photobucket.com/albums/z224/A26B/Tach%20Connection_zpstuflmgat.jpg (http://s190.photobucket.com/user/A26B/media/Tach%20Connection_zpstuflmgat.jpg.html)

[9T1 Red ZR1]

Thank you Jerry, that is a big help!

Bill