Mph difference?

[jb'sWS6]

This is for a friend of mine's car. He went to the track Friday nite to run his car after buying slicks. His previous best was 11.9 at 124mph w/2.2 60 ft. time. With slicks and no other changes he went 11.4 at 112 w/1.5 60 ft. time. Now his car is an 04 Cobra w/a Kenne Bell supercharger and I know this is an ls1 board but usually him and I go together and I take my car too. Soooo, I'm hoping you all will overlook the blue oval and look at the question in general. Has this happened to anyone else? He didn't notice the car running any different (no codes thrown or ses lights). What would cause a 12mph difference in trap speed? That screams horsepower loss to me but I wasn't there. Any opinions would be appreciated.

[Empatho]

the better the 60 foot time the lower the MPH, if you spin allot you get higher mph and if you hook you get a lower mph

[jrgswhitels1]

I wonder if he was bogging out of the hole? You can lose some power when engine load is greater than your tune was allowed!!? There is some concern there though !!

[Mr. Luos]

I would say bogging as well.

[98ls1blackbird]

It also could be the slicks are taller and killed off some of the gear ratio. You are right, it should have mph'd in the same range.

[jb'sWS6]

I didn't think to ask him the height of his new slicks. As for launching he said he worked his way up to leaving right off redline (6000+ RPM). I just asked his 60 ft. time, didn't think to ask if it was bogging. He was worried that the belt for the supercharger was slipping but did not pay attention to his boost gauge while going down the track. He is still trying to get the hang of driving the car at the track at mainly watches tach so as to not mis-shift. I'll try to catch up with him today and get back to you all.

[BLKCLOUD]

You do not lose 12 mph going from street tires to slicks. In fact, I typically run about the same mph - and sometimes better - with better traction. I'm sure he probably did bog....a little, but not enough to make a significant difference.

What happened? Malfunction on the ET lights? He let off a little early? Who knows. Post the timeslips so we can see more than just the 1/4 mile. The 1/8th ET/MPH would be most helpful.

[jrgswhitels1]

TRUE THAT!!! I can see 1 or 2 mph, maybe even 3 mph difference in trap speed with/ without drag radials, but 10 or more!, man-oh-man somethings not right? Timing, boost, etc!!!!!!! That WILL kill some power if not set to your tune or set-up!! There a buddy of mine who has a twin turbo Viper, he has a variable boost controller in his ride. He tells me he plays with the boost ALL the time depending on who he races!! He made a critical mistake running a sport bike and forgot how low his boost setting was and endded up over-revving 2nd gear thinking he was on full boost!! Well, its up in his hoist at his shop with the blown motor pulled from it!! He is really pissed at himself for forgetting. Sometimes it easy to forget the simple things that get overlooked often!!??

[LS2Tuner]

This is for a friend of mine's car. He went to the track Friday nite to run his car after buying slicks. His previous best was 11.9 at 124mph w/2.2 60 ft. time. With slicks and no other changes he went 11.4 at 112 w/1.5 60 ft. time. Now his car is an 04 Cobra w/a Kenne Bell supercharger and I know this is an ls1 board but usually him and I go together and I take my car too. Soooo, I'm hoping you all will overlook the blue oval and look at the question in general. Has this happened to anyone else? He didn't notice the car running any different (no codes thrown or ses lights). What would cause a 12mph difference in trap speed? That screams horsepower loss to me but I wasn't there. Any opinions would be appreciated.

The high trap speed with the other tires was do to spinning so bad.
11.90's should NOT be anywhere near 124 mph.
It called dead hooking and blowing the tires off with boost period.
If it has a tall slick on it the tire grows on the big end also.
Yes the speed is lower than expected but there can't be too much of a hp loss with a 1.5 60 foot. Those cars are not light by any means.

You do not lose 12 mph going from street tires to slicks. In fact, I typically run about the same mph - and sometimes better - with better traction. I'm sure he probably did bog....a little, but not enough to make a significant difference.

What happened? Malfunction on the ET lights? He let off a little early? Who knows. Post the timeslips so we can see more than just the 1/4 mile. The 1/8th ET/MPH would be most helpful.

What happened the car hooked. You think 11.90's @ 124 is anywhere near normal......NO it's not. It should of been around 113-115.
The 11.40 should be around 118-121 range.
He could of short shifted on the big end without taking the growth into consideration. The possibility's are endless. The info is WAY too vague and not to mention he wasn't even the driver.

[BLKCLOUD]

The high trap speed with the other tires was do to spinning so bad.

What? And you know this how?

11.90's should NOT be anywhere near 124 mph.

With a properly setup car, sure. With the average internet Joe's car? Seen it many times. Saw it at Norwalk Friday.

You know what else? 11.4 @ 112 ain't normal either. Not even for a purpose-built Stock/SS Eliminator car.

It called dead hooking and blowing the tires off with boost period.

OMG. Go do some real drag racing. "Period".

You're not going to gain or lose 12 mph simply because of the difference between a "dead hook" and "blowing the tires off". Additionally, my experience is that the "blowing the tires off" pass would have a worse MPH than the "dead hook" pass. You *may* see a bit higher mph with some spin off the line - but not "blowing the tires off".

If it has a tall slick on it the tire grows on the big end also.

Sure. And kills the gear. Which should also kill the 60 ft. And probably the whole run. But it WON'T cost the car 12 mph.

Yes the speed is lower than expected but there can't be too much of a hp loss with a 1.5 60 foot. Those cars are not light by any means.

I cannot believe someone that claims to be knowledgeable on this stuff is trying to blame a 12 mph decrease on good traction.

Reader beware.

What happened the car hooked. You think 11.90's @ 124 is anywhere near normal......NO it's not. It should of been around 113-115.
The 11.40 should be around 118-121 range.

Once again - this is someones STREET CAR. Not a race car.

And please lecture me on what is 'normal' and 'not normal' for ET/MPH package. I'm drag racing rookie. Really.

He could of short shifted on the big end without taking the growth into consideration.

A car running 124 mph is NOT going to have a lot of tire growth at the big end. Not enough to make a 12 mph difference. Not even sort of.

The possibility's are endless. The info is WAY too vague and not to mention he wasn't even the driver.

Well golly Wally, on this we can agree.

What's not too vague is the crazy idea that it was simply traction related.

[jrgswhitels1]

Damn dude,LOL!!!!!! Easy on the BELTING!!!! LOL!!!!! Sometimes (Who me?)people take their ride to the track to just to see if they can hook on new suspen. mods. or something and let off at the end to see if theyve improved on thier 60ft. or 1/8th mile run! Many of us disguise our true run for the simple sake of keeping other thinking! Especially if you have local hangouts! You know there's always going to be a snitch! "Hey, I seen that car at the track the other day, you know it runs mid 11's"!!!!!! You know the rest.

[jrgswhitels1]

Little would anyone know, its a mid 10 car!!!!! Where's my money..... biatch!!!! Look at you ALL just laughing!! I know you probably heard of many situations like this!!! LS1's RULE forever!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!

[00maroz28]

the 2.2 60ft... suggests spin out of the hole... when you spin that much out of the hole your mph will be higher, that much higher? idk.., not on a stock car but a car with that much power to run in the 11's maybe

the other car ran 11.4, but with a 1.5 60 ft! thats great that is a really good launch, hence the lower et but lower mph

but what do i know

heres an example on a smaller scale... my best time was 12.8 at 108. with a 1.9 60ft, later that night i ran a 13.2 at 113 with a 2.4 60 ft. because i smoked the tires out of the hole, while trying a new launch style (which didnt work too well lol) mph miuch higher but slower et... same thing that happened to you but smaller scale... but there's 5mph difference on a 12.8 car so 12 mph on a 11.90 car maybe, still a little far fetched though but not impossible

[LS2Tuner]

What? And you know this how?


With a properly setup car, sure. With the average internet Joe's car? Seen it many times. Saw it at Norwalk Friday.

You know what else? 11.4 @ 112 ain't normal either. Not even for a purpose-built Stock/SS Eliminator car.


OMG. Go do some real drag racing. "Period".

You're not going to gain or lose 12 mph simply because of the difference between a "dead hook" and "blowing the tires off". Additionally, my experience is that the "blowing the tires off" pass would have a worse MPH than the "dead hook" pass. You *may* see a bit higher mph with some spin off the line - but not "blowing the tires off".


Sure. And kills the gear. Which should also kill the 60 ft. And probably the whole run. But it WON'T cost the car 12 mph.


I cannot believe someone that claims to be knowledgeable on this stuff is trying to blame a 12 mph decrease on good traction.

Reader beware.


Once again - this is someones STREET CAR. Not a race car.

And please lecture me on what is 'normal' and 'not normal' for ET/MPH package. I'm drag racing rookie. Really.


A car running 124 mph is NOT going to have a lot of tire growth at the big end. Not enough to make a 12 mph difference. Not even sort of.


Well golly Wally, on this we can agree.

What's not too vague is the crazy idea that it was simply traction related.

I won't even waste my time....Obviously you can't read.
I'll be at the track anytime you want to get beat out west here.

[BLKCLOUD]

LOL. Ya, I'll drive right out there so you can school me. Thanks for the invite!

And I can read just fine, thank you very much. Please, waste a little time and tell me where I have gone astray. Personally, I think you won't waste your time because you know - you HAVE to know - that you don't lose 12 mph just from "dead hooking", as you stated.

Of course I'm assuming you're not that dumb.

Then again, I've been wrong before....and gee whiz, he might not of taken tire growth into account (damn tire growth threw off the tach I guess).

Bob

PS.....uh......Period.

[LS2Tuner]

The 11.40 should be around 118-121 range. Period as said the first time.

Good thing you have talked to the driver telepathically. Glad you got it figured out for him. We need more like you on here that's for sure!

[BLKCLOUD]

The 11.40 should be around 118-121 range. Period as said the first time.

I see. And so this guy only ran 112 mph because he "dead hooked"? "Period"?

I've run 11.4 @ 115 mph w/1.60 60 ft. Full throttle pass all the way down the track. At 121 mph, I'd fully expect to be in the 11.0s. So what was/is wrong with my car?

No "dead hook" btw. That was on DRs.

I've also run much slower ETs at a much higher mph with a much worse 60 ft (different car). So what "should" would apply to that situation? And if I "dead hooked" on one of those 120+ passes, would l lose 12 mph?

And tell me....how many cars have you seen make full throttle passes that went 11.4 @ 112 mph? Even those that "dead hooked"?

Good thing you have talked to the driver telepathically. Glad you got it figured out for him. We need more like you on here that's for sure!

Speaking of not reading posts....you'll note that I gave a couple things that it *might* have been, and that I also said we need more data. Shall I quote myself for you to read again?

However, your posts were crystal clear. "Period". The problem is, you're clueless. For evidence, one only has to read them.

Bob