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Discussion Starter #1
A little background first.

My car is a mild 306. Performer 1.9/1.6 heads, explorer intake and a comp XE270 cam. 2.95 first T5 with 3.73s. Car is close to full weight 90 gt. (no AC and glass hood). I'm running on 26x9 Hoosier QTP. The one thing I have been really happy with is my car has been pretty consitant. I don't normaly change anything other than tire pressure at the track and usally all runs are with in a tenth. I have my shift light set at 5500 rpm. I leave on the shift light to keep things "easy". Sixty foot times are usally around 1.75 with ETs in the the low 12.8s high 12.7s. Car would hook hard and felt like it would twist like a pretzel. Like it was trying to put the right rear thru the track surface.

I swapped in an aluminum flywheel after a bunch of reseach. I found some tests on a car simuliar to mine. They ended up having to raise their launch rpm from 4500-5000 to keep 60ft times the same, and ended up about a tenth quicker. That sounded good to me since I've always felt like I was launching higher than needed just to make staging and launching easier.

I finally made it to the track and the first thing I noticed was it was much harder to hold launch rpms steady, but that makes sence with the lower rotating weight. My 60 ft slowed by a little over a tenth, and my ET slowed the same tenth leaving at 5500. The car didn't feel like it was luanching near as hard. Kind of felt like it was spinning a little. I dropped the rpm to 4500 and went back to a 1.76 60 ft time. Launch felt a little better, but still not as hard as before.

When I swapped in the flywheel I also swapped the stock clutch for a King Cobra clutch, and swapped the stock drive shaft for the FMS aluminum one.

Is it possible that I'm getting more wheel speed quicker and loosing grip, or is the lighter weight hurting the car? Based on dropping the rpm and getting the 60ft back. makes me think I can do better with the Alum piece at the higher rpm. Maybe more tire to hold it?

What do you guys think?

TIA.
 

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I went through this exact same thing a while back! My research was what made me stay away from the alum flywheels! They are more for high HP light weight cars or street use. I have read that they were mainly designed for road race applications. A heavy car needs the weight of a steal flywheel to launch it out of the hole! Do some more research and you will see! GOOD LUCK
 

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I think you needed the heavier stock flywheel to get your car to launch...the extra mass keeps the inertia up to get that heavy car to launch. The boards that you read and guys that you talked to with the Aluminum flywheels - where these car light cars or stockers like yours.

I put an aluminum flywheel in my notch and it only weighs 3150 with me in it and I noticed that I had to launch higher to keep my 60 fts....a heavy car like yours needs all the mass it can take to get her rolling.
 

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its the inertia of the spinning mass that you lost its like losing torque, but leaving alittle harder should make up the difference plus you should gain some upper rpm hp ! it should be faster but not worth the money in my opinion and the 373 arent helping you, i would atleast run 4.10's or 4.30's with a aluminum flywheel to help the loss of torque ! did you pick up any mph ?
 

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This is good info... Makes me wonder what would happen to my car if I swapped in a steel flywheel... Mine weighs 3,120 give or take 10 pounds...

I know I have to launch my car pretty hard to get a good sixty foot out of it... on 26 x 8.5" slicks, I've been 1.56 short time launching at 5,700....that was on a superb hooking track... the normal sixty is 1.61, launching around 5,300-5,400.....

It makes sense that the steel flywheel would propel the car on the launch... I guess it's just more pronounced with a car that weighs more....

I vote for the aluminum flywheel.... I think they are worth power.... If I gotta launch 400-500 rpm's higher to get the sixty foot, then so be it..
 

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Discussion Starter #6
I put an aluminum flywheel in my notch and it only weighs 3150 with me in it and I noticed that I had to launch higher to keep my 60 fts....a heavy car like yours needs all the mass it can take to get her rolling.
Thats the part that is driving me crazy. I DROPPED launch rpm to get my 60 ft back. Makes me think I might be spininng a little.

As for mph I really can't say do to a pretty good head wind Saturday. I was a couple mph slower, but some of my buddies were as much as 5 mph slow. So its still up in the air as to if I gained any top end.
 

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I did the same swap on my stock HCI '89 gt and it lost some et and mph. I could get the car to .60 the same but i came to the conculsion that i was losing "inertia" on the 4th. gear shift at the traps (1/8th.)........car may have went quicker in the 1/4 which would give the AF time to gain back the lost ground on the gear change.........my car is also roughly 2900lbs race weight.

MM&FF did a test about 5 years ago with Robin Lawrence's FS car and another real street style blower car.............dyno and track test between AF/light clutch vs. stock weight stuff. Both cars picked up a bunch, especially the blower car BUT they were losing up to 40hp on the gear changes until the AF/clutch would "catch" back-up and show roughly a 14hp gain (Robins car) through out the rpm range (6500+). The AF/clutch was also worth roughly a tenth in the 1/4 on Robins car @3200/3300lbs............

I went back to a heavier (4lbs. over stock) RAM wheel and the car went right back where it was (7.70's) and mph went back up as well. I think besides weight, rpm is a huge factor in the AF showing its worth IMHO..........hopefully someone with a little more "practical" knowledge will chime in:)
 

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Let's not forget you changed your clutch too. That's probably effecting your launch at least as much as the flywheel if not more. Mabey you're spinning because the new clutch is holding where the old clutch gave a little, which was helping the chassis and tire work. You're going to have to get a new base line for the car before you can determine whether you picked up or lost anything. It's not clear in your post if you're using a 2-step. Without that you're just guessing what rpm you're leaving at. I would give it at least a few trips to the track and try lots of rpm, tire pressure, and burn out combinations before I would make any judgements. I bet it will pick up once you figure it out.
 

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Discussion Starter #9
That's what I'm thinking (or maybe hoping is a better word. lol) I'm going to borrow some 26x10.5 MT et streets and see if that changes things at all. Just wish I had more time to go to the track than once a month.
 

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Just wish I had more time to go to the track than once a month.
Be happy you get to go atleast once a month........ i wish i could go more and i wish there were a track that were closer than 1:30 away !

the flywheel didn't hurt you any you just have to figure your car out all over again. just like me i broke my pinky toe now i have to learn to drive all over again, you would believe how important that toe is till you can't use it...... LOL
 

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Discussion Starter #11
The track I go to is about 1:15 away so by the time I pay for gas to and from plus entry it gets to be a spendy day outta the house. lol
 

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Discussion Starter #13
nothing is "wrong" with Martin itself. It's a pretty nice place. I've been going to Stanton since it was called Central Michigan Drawway. It just seems to be a freindlier place for us "litle guys" than Martin.
 
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