JL ws-6

iTrader: (50)

I know your car LOL. Seen it there long time ago back when I first started dealing with them, I couldn't believe how that thing ran!

You know who to get ahold of to get in contact with Ultimate then.

bad2000z

iTrader: (4)

Anybody know the answer to my question earlier? I'm guessing 6500-6600rpm?

JL ws-6

iTrader: (50)

Depends on the converter, how effecient is it on the top end?

bad2000z

iTrader: (4)

I'm not sure? How do I determine it's effeciency? I feel like a newbie again LOL.

JL ws-6

iTrader: (50)

Go to the track, run the car. Log, or read the RPM off a good tach going thru the traps.

Now when you have your timeslip, you have to do some math.

Take the tire diameter (with groth factored in if it's a bias ply) multipily that times 3.14159. That is the rollout of the tire in inches. Convert that to feet (divide by 12)

Now take the mph, convert that to feet per min. Take the mph, multiply that by 5280, that's the # of feet per hour. Divide that by 60 to get the # of feet per min.

Now, take the rpm going thru the traps. Divide that by the rear end ratio, and you have the # of RPM the axles are turning. Now take the rpm the axles are turning, and calculate the feet per minute that the tires "should" be doing. You know the tire rollout in feet from the previous calculation, multiply that by the axle rpm that "should" be happening.

Now divide the 2 #'s and get a %. Any decent converter shoudl be under 10%, better then that if it's something that was built specificially to the car. If you come up with a # like 20%, you have a slipping tranny, are totally blowing thru the converter, something is way off. If you calculate that it's at 3%, then you probably would benefit from a looser converter.

If you are "locking" the converter during the run, then this calculation will tell you if teh tranny is slipping, or if the converter isn't locking up right.

Now this isn't absolutely perfect, because the mph is an average across the end of the track, so there's a little fudge room, but it will tell you if something is way off.

bad2000z

iTrader: (4)

OK, I won't make it to the track until at least April 13. Let's say for arguments sake the effeciency is...9%. How do I calculate what my RPM's will be going through the traps at 120-121mph? Thanks JL.

StreetStalkerZ

iTrader: (1)

Your other option on the 28" tire would be to step the gear up slightly (4.30s)?

I'm going to convert back to a 28" drag radial with 4.30s to compensate for the added tire height. IMO a 4.30/28" is about the same ball park as a 3.90/26" tire. But i have a motor that can spin to the moon so running high RPM across the traps is not a factor to me.

bad2000z

iTrader: (4)

I was actually contemplating the same thing.

JFM-jr

iTrader: (23)

Not sure what I am missing here but
3.90 on a 26" tire = 141 mph@7000
4.30 on a 28" tire = 136 mph@7000
these are basic numbers from an A4 using the calculater in the gears/axels forum. 6mph difference is alot in my book

JFM-jr

iTrader: (23)

I used a 26.4 in the calculater as Hoosiers site lists the 26 actaul diameter at 26.4. These figures from the calculater are locked in 3rd gear @ 1:1 so i'd assume unlocked figures would vary according to converter somebody correct me if I am wrong (please).

StreetStalkerZ

iTrader: (1)

I don't go completely by that. Weight,converter slip,DA all play a role in mph and ET. I'm confused because in one post you said that only adding 28" tire will give you more MPH but if your running out of gear then that is what you want but if your wanting to compensate for the added tire then more gearing is what your will need??

When i had the PT4400 and 4.10s i was crossing the traps at 6900 rpms on 26" drag radials but with the 28" drag radials i was crossing barely at 6600 rpms. If your running out of gear at 6500,like your earlier post stated, then your transmission could be slipping on the high side more than you think.

JFM-jr

iTrader: (23)

going to a 3.90 on my current 26's or leaving the 4.10 and using a 28 would get me nearly identical results. In my current configuration i'm nowhere near 6900 rpm's at the traps (I'm at 6900 well short). NHRA Formula seems to be in the same boat as me. I have a brand new tranny in my car car Performabuilt level 3. I doubt it's the problem as much as I doubt the stock trans I took out was the problem either. What kinda numbers did your car run out of curiousity?

JL ws-6

iTrader: (50)

I still think you'd be best off going to the 28 inch tire and another set of 4.10. The added traction/ability to run more air pressure because the tires will work alot better IMO will net bigger gains in the long run.

A set of 275/60/15 drag radials might be something to think about, the radials generally like abour 18 pbs of air so you'll have a good stable top end, and teh top end mph with radials always seems better. Plus if you're leaving off the footbrake, the radials will probably work good, I had great luck running them off the footbrake last year. Not so much so off the transbrake though

StreetStalkerZ

iTrader: (1)

With my cam only setup i went a best of 7.04@98.8mph 1/8th mile with a 1.47 60ft. through the 1/8th mile. I blew the stock motor up the next week lol. With the motor letting go at the 1000ft. the next weekend it went a 11.26@116 with a 1.48 60ft. costing from the 1000ft. to the 1/4 mile. DA was around +1000,not much to compare to because that setup was nothing like yours.

I have a completely different setup now and im in the process of changing out the gears back to a 4.11 from 3.70s. I need more rpm through the traps,only crossing around 6200-6300 rpms. Maybe i'll have all my ducks in a row and crank out some ETs on motor like yours and JL-WS6's. I had alot of bugs to work out and i think most of them are going to be solved but im still stuck with a LS6 intake