von

Ok I have done mild to agressive manifold porting on my 89GXL with 20k on rebuilt engine stock port. I also have sleeves (pineapple) that are cut shaved and J/b welded into block. TB mod , coolant line , e fan pulleys 200lbs weight reduction and custom short intake with streight pipe bonez exaust... Sooo

Well I still dont brake the tires loose at 6k like you said you did. IS YOUR 7 STREET PORTED??? Dood im getting really disapointed. Everything I do I cant seem to notice any difference and its pissing me off. My manifolds look like yours. I mean yeah I have no headers and no S-AFC ( I do but its not running yet) BUT you said that headers are MINIMAL GAINS. so like wtf. Are cars are the same damit. I mean I feel a slight difference at 6k but hardly anything. The car does seem to rev to 8k before power drops off but I get no kick at all. just really flat. After AFC and Headers and TB porting im geting this **** dynoed and if I get under 150rwp with a kick in the pants then im giving up.

Any N/As out thier want to race me for a mod check???

wankelhead

i guess i have some questions myself.i mean,as far as tire spinning,it of course has a lot to do with the rubber on the back.but,my car,on dry pavement,has definately never let go at high rpm.i dont know if,once a rotary is broken in,it will continue to build compr. for a few thousend miles[like boingers],in wich case i might build up a bit more power,as i only have apr.1500 miles on my rebuild.i just started taking it up to 7k,and while it continues to pull,i cant say it really pulls harder in the 6-7k range.i have not adressed my fuel yet,thou.i think the portland rx7 club is having a dyno day in a month or so near me,so i might try and make it there.i still have some hesistation probs to adress and stuff,thou,so the jury is still out.anyway,just keeping this thread going.
d

Rxmfn7

iTrader: (4)

You have to remember also that Mazdaspeed7 has FB gears, which are way lower than ours. I hope to get some on my FC soon, as he says it will help immensly. This weekend I am porting my manifolds and installing my RB header and pineapple sleeves, and while I hope for a noticable improvement, I highly doubt that I will spin the tires at 6k.

nitroracer

iTrader: (5)

i spin my tires when i rev to 4.. and i have 225 in the back

Rxmfn7

iTrader: (4)

Do you mean revving and dumping clutch, becasue I believe we are talking about the tires just breaking loose under acceleration. Unless you have a turbo...then shut up

bcty

just when you are accelerating they break loose.. i get 3rd gear rubber if thats what your talking about.. u must have some mad power to just break loose when your driving?!

Ichiban

well as i previousely mention went for a ride in a mates 10 second turbo II with 500hp @ rear wheels breaks traction so easy dropped it into 3rd going about 90 miles and light them up

mazdaspeed7

I *had* bald, shitty tires and an open diff. Now I have a LSD, and really good tires, and I dont spin them. The other day I dropped my clutch at 5000 rpm, my car spun for half a second, then bogged to 3000 rpm, and took off. I cant wait to get to the track, I want to see what kind of 60 ft I can pull now.

It really depends on your tires. I cannot keep my tires spinning on dry pavement anymore, theyre just too sticky. I have Dunlop SP Sport 8000's, sized 225 50 zr 15 on the back.

FC3AZ

hey Mazdaspeed, can you get a pic of that size tire on the 15" rim for me. I am considering some tires of that size and wanted to know what they would look like. Thanks.

mazdaspeed7

Ill get a better pic later.

FC3AZ

thanks a bunch, that size tire looks good on that rim.

von

The tire thing makes sense I guess. I forgot to mention that I have 215 60 15s yokohamas.

Ok what I do know is I can chirp the tires when when I hit it in first gear at 5-6k rpms. Like I sit thier at that rpm then I just jab the throttle. It will chirp momentarily. I guess Im doing pretty good then. Im sure the porting will become more evident when I hook up the S-AFC because of the extra fuel that counteract some of the effects of porting... Hope this makes sense? Anyways I can imagine my car with a tuned afc. Some people say it gives 8-10hp on a car modded like mine. Hopefully I will spin the tires wile WOT ( not dumping or shifting) Headers wouldnt hurt either. My sliping cluch is really bad but I can still chirp when I dab the throtle , its just when I shift I get tons of slip.

mazdaspeed7

Why do you want to spin your tires so bad anyways?

von

It was just a thought. And sort of big payoff for all the work I did on my car but I guess my tires are to sticky for my current setup anyways. It also means im making lots of top end but after the porting I dont feel a rush anymore top end , I think because it gave me a flater and smoother power curve.

Mazdaspeed7 , were and how do I get FB gears?

mazdaspeed7

I can build you a tranny. PM me if youre interested.

von

oh crap I didnt know it was a tranny. I thought it was a differential. Anyways how much would one cost for you to make?

wpgrexx

i have toyo proxes 205 40 16, if i am in first clutch out, drive to 4000rpm, and then punch it, i can spin the tires all the way up to 7500(stillmakes power to 8000, but its s4 so it isn't that great of thing to do.) when i shift to second they chirp and then go. try advancing the timing a little to get a little more power. My car used to run shitty at powershifts at 7500, advanced the timing, no problems anymore... Yaaaaaaaaaaah

von

yeah I was thinking of 20 dagrees.

von

yeah I was thinking of 20 dagrees.

3engineRex

nice, theres actuall a lot of good info in a thread for a change. i really love learning everything i can about well pretty much everthing.

mazdaspeed7

I guess Ill post it here too. I made an excel spreadsheet about the FB tranny swap. Definately worth reading if youre interested.

Heres the excel spreadsheet

von

ok saved it and looked at it and its very helpful but I was thinking wouldnt 4.3 gears over 4.1 work almost the same as the 85 fb tranny? Seems like thier just about the same but I think I have another one of your spreadsheets with the final drives . hold on

von

Mazdaspeed7 Ok I just found out something interesting using a gear ratio chart.

First off FB gears in THIRD gear are 1.42 or something.
This means at 8500 rpm you reach 100 mph finishing the 1/4.
Now at 8000 rpms im at 100mph in third with 4.1 gears and finishing the 1/4. So then I put 8500 rpms in at 100 miles an hour and got a final drive ratio of 4.34 over my 4.1 Meaning that a 4.3 gear and pinnion set are almost exactly the same as an FB tranny for the same mph and rpm. Very interesting. Mabey someone can do this to see if I miscalculated something?

von

If that was confusing then let me put it this way. Basically using FB gears and 4.1 tranny is the same in the 1/4 at 100mph that using 4.3 gears on a stock tranny. Get it?

mazdaspeed7

1st and 3rd gear on the FB tranny are about the same as the FC tranny with 4.1 gears. But 2nd is still a lot shorter than an FC tranny and 4.3 gears. And 5th is simply unbelievable. My car pulls nearly as hard in 5th as it does in 4th.


btw, i used this equation to figure all that out


mph=(tire circumference x rpm)/(transmission ratio x rear end ratio x 1056)

My tires are 23.5" diameter, which comes out to a circumference is 73.79" The stock tires are 24.5" with a circumference of 76.93"