hey, what up? i know a 20b swap isnt a chead or easy thing to do with a fd, but i was wondering something.



how much more does a 20b weight than a 13b??? does a 20b into a fd really mess up the great handling of the fd???

[quote name='pushnlacs' date='Mar 21 2005, 03:11 AM']hey, what up? i know a 20b swap isnt a chead or easy thing to do with a fd, but i was wondering something.



how much more does a 20b weight than a 13b??? does a 20b into a fd really mess up the great handling of the fd???


[/quote]



my car lost 60lbs when i went back to a 13b

you had a 20b and went back to a 13b? can i ask why? was it for handleing?



i am suprised the 20b only weighs 60 lbs more than the 13b, that really isnt to bad and i wouldnt think 60lbs would throw off the handleing to bad.



hey the RE gt300 uses a 3 rotor and jgtc cars need to handle real good.

I've heard on other websites that the 20b can actually shed some weight, any truth to this?

[quote name='pushnlacs' date='Mar 22 2005, 02:01 AM']you had a 20b and went back to a 13b? can i ask why? was it for handleing?



i am suprised the 20b only weighs 60 lbs more than the 13b, that really isnt to bad and i wouldnt think 60lbs would throw off the handleing to bad.



hey the RE gt300 uses a 3 rotor and jgtc cars need to handle real good.


[/quote]

Apparently the 20b pushes the steering rack to a different location which causes bump steer, which would affect the handling somewhat. To be honest I can't see how this couldn't be solved with a new rack - it's not like the 20b guys are on that tight of a budget https://www.nopistons.com/forums/pub...IR#>/dunno.gif



Mark

I compared the weight of a 20B almost literally part for part to an old style 4 port 13B from my REPU and if I move the battery to the back, my front end may just about break even. I could hardly believe it myself. Of course I am not using the stock twins, so there's a weight savings on 62lbs right there. Infact, my header weighs the same as a stock 13B exhaust manifold from an R5 (JDM Luce or Cosmo) engine. Both weighed 21lbs or so, yet my header shifts its weight much further rearward for less weight directly over the front wheels.

so even with a 20b, the fd would still be one of the best handleing cars out there huh?

So long as you don't have to get rid of your front sway bar, sure.

You'll still have the bump steer problem though..... the only real solution to that from what i've seen is moving the engine/tranny rearward....

Even though it's a full blown race car, the RE-Amemiya FD with the 20b seems to handle pretty well...Of course they have a bigger budget than most anyone dealing with a rotary.

I want a 20B.

My engine supplier wants a down payment. https://www.nopistons.com/forums/pub...1047683358.gif

[quote name='Il RX8 lI' date='Mar 22 2005, 07:20 PM']Even though it's a full blown race car, the RE-Amemiya FD with the 20b seems to handle pretty well...Of course they have a bigger budget than most anyone dealing with a rotary.


[/quote]



that car is most likely a full tube chassis car.. You can't even consider it an FD anymore.

[quote name='pushnlacs' date='Mar 21 2005, 05:01 PM']you had a 20b and went back to a 13b? can i ask why? was it for handleing?



i am suprised the 20b only weighs 60 lbs more than the 13b, that really isnt to bad and i wouldnt think 60lbs would throw off the handleing to bad.



hey the RE gt300 uses a 3 rotor and jgtc cars need to handle real good.


[/quote]



i had computer problems, it left me stranded one too many times.



it does handle better with the 13b, but thats cause i have a front swaybar again.



the re car isnt really much of an fd anymore, the engine is way low and far back.

[quote name='GreyGT-C' date='Mar 23 2005, 12:29 AM']You'll still have the bump steer problem though..... the only real solution to that from what i've seen is moving the engine/tranny rearward....


[/quote]

I'm not looking for an arguement, but that really sounds like a backwards way of eliminating bumpsteer - I'd love to see some decent pics of a 20b install with this problem.



Mark

[quote name='inanimate_object' date='Mar 23 2005, 01:50 AM']I'm not looking for an arguement, but that really sounds like a backwards way of eliminating bumpsteer - I'd love to see some decent pics of a 20b install with this problem.



Mark


[/quote]



well on the fd the front rotor on a 20b and the steering rack would share the same space, so you can either move the rack, and get bumpsteer, or move the engine back and refabricate the trans tunnel and ppf. option 3 would be to just raise the front of the engine up, but then it would be poking thru the hood.



mazda had 20b fc's running around in 88-89, motor trend tested one, they knew they didnt want the 20b to fit in the fd so they made it harder.

i heard mazda had plans to possibly put a 20b into the fd.

[quote name='j9fd3s' date='Mar 24 2005, 03:22 AM']well on the fd the front rotor on a 20b and the steering rack would share the same space, so you can either move the rack, and get bumpsteer, or move the engine back and refabricate the trans tunnel and ppf. option 3 would be to just raise the front of the engine up, but then it would be poking thru the hood.



mazda had 20b fc's running around in 88-89, motor trend tested one, they knew they didnt want the 20b to fit in the fd so they made it harder.


[/quote]

Why can't you leave the engine there, move the rack forward and replace it with one that's the right length to get rid of the bumpsteer?



Mark

[quote name='inanimate_object' date='Mar 24 2005, 03:56 AM']Why can't you leave the engine there, move the rack forward and replace it with one that's the right length to get rid of the bumpsteer?



Mark


[/quote]



um i dunno? i used an fc, which doesnt have that issue

Thats a good point.



Cody

You'd be replacing bumpsteer with other, even more insidious steering issues.



Instead of moving the engine rearwards, I'd move the whole subframe forwards. This would require new inner and outer fenders and a new steering column, and handling wouldn't be as snappy due to the longer wheelbase, but you could always just relocate the rear axle as well.



"I never liked to do things simple when I could do them ass-backwards". Bonus points for ID-ing that quote.

[quote name='heretic' date='Mar 28 2005, 02:30 AM']You'd be replacing bumpsteer with other, even more insidious steering issues.
[/quote]

Like what exactly?



Mark

[quote name='inanimate_object' date='Mar 28 2005, 03:24 AM']Like what exactly?



Mark


[/quote]



Assuming you could get the bumpsteer near correct, since hanging a rack is a non-trivial job and you would additionally have a lot of diddling to do with rack lengths, you would suffer from horrid amounts of negative Ackerman.



If you picture a car driving around a corner, you can see that the inside and outside front tires will have to describe two different arcs, since the inside tire will have a shorter radius in the corner than the outside one. Without getting into too deep of an explanation with lots of diagramming and such, if you move the rack forwards, the inside tire will not turn enough relative to the outside tire.



If you've ever wondered why 80's Mustangs felt so odd when cornering, like the harder you drive the less the steering felt sure, that is why. There is a large market for fixes for this, and a lot of road racers extensively modify the subframe to both get the rack as far back as possible, and the ball joints as far forwards as possible, assuming they don't just buy a pre-made custom job.

[quote name='heretic' date='Mar 29 2005, 02:00 AM']Assuming you could get the bumpsteer near correct, since hanging a rack is a non-trivial job and you would additionally have a lot of diddling to do with rack lengths, you would suffer from horrid amounts of negative Ackerman.



If you picture a car driving around a corner, you can see that the inside and outside front tires will have to describe two different arcs, since the inside tire will have a shorter radius in the corner than the outside one. Without getting into too deep of an explanation with lots of diagramming and such, if you move the rack forwards, the inside tire will not turn enough relative to the outside tire.



If you've ever wondered why 80's Mustangs felt so odd when cornering, like the harder you drive the less the steering felt sure, that is why. There is a large market for fixes for this, and a lot of road racers extensively modify the subframe to both get the rack as far back as possible, and the ball joints as far forwards as possible, assuming they don't just buy a pre-made custom job.


[/quote]



Getting the rack length is simple, you keep the track rod ends in line with the suspension mounts that's all there is to eliminating bump steer. As for the ackermann problem, horrid amounts? how far forward do you have to move it? With a 20b you probably want a bit less Ackermann than stock since you'll be going that bit faster.



Mark

The phrase "easier said than done" comes to mind. If the rack needs to be lengthened, that can be done fairly expediently, but if it needs shortened, that's a bit more difficult to deal with.



I don't understand why you'd want to compromise the steering because the car can theoretically go faster. Won't be able to go faster in corners, anyway.



By the same token you could say that bumpsteer is not a problem because you will be using 1000lb-in springs and the suspension will barely be moving.



Also by the same token, you could say that a little reconstructive surgery on the firewall and modifying the driveshaft and PPF is much preferable to screwing around this way and that with the frontend. As a bonus, you get to shift some weight rearwards, never a bad thing. Might even compensate for the huge front-mount intercooler and huger radiator you'd probably want to install, too.

[quote name='heretic' date='Mar 30 2005, 01:21 AM']The phrase "easier said than done" comes to mind. If the rack needs to be lengthened, that can be done fairly expediently, but if it needs shortened, that's a bit more difficult to deal with.

[/quote]

It's no harder to shorten the rack, the guys building the same car as is in my sig shorten the rack in their own garages without any hassle. If it's a hardened rack, generally it's just the teeth that are hardened so that's not a problem. And that's not even touching a custom rack or finding a suitable donor one which are both viable.



[quote name='heretic' date='Mar 30 2005, 01:21 AM']I don't understand why you'd want to compromise the steering because the car can theoretically go faster. Won't be able to go faster in corners, anyway.

[/quote]

I'm not talking about comprimise, chances are the 20b is not the only alteration to the car, chances are you're running bigger softer tyres too, and with the 20b you're hitting the corners faster, you probably want less Ackermann.



I'm aware there's a trade off between better roadholding and fidgity steering, but that only happens when you get into negative Ackermann. I don't know what amount of Ackermann an fd has, I'm assuming it's positive by some amount, leaving some room for moving the rack, worst case scenario you lengthen the steering arms on the uprights.



[quote name='heretic' date='Mar 30 2005, 01:21 AM']By the same token you could say that bumpsteer is not a problem because you will be using 1000lb-in springs and the suspension will barely be moving.

[/quote]

Very true, but if it can be fixed, then why not?



[quote name='heretic' date='Mar 30 2005, 01:21 AM']Also by the same token, you could say that a little reconstructive surgery on the firewall and modifying the driveshaft and PPF is much preferable to screwing around this way and that with the frontend. As a bonus, you get to shift some weight rearwards, never a bad thing. Might even compensate for the huge front-mount intercooler and huger radiator you'd probably want to install, too.


[/quote]

But what is a perfectly good car worth after all this? Although that is a fair point about shifting the weight back.



I guess we're coming at this from different angles, the real benefit of changing the rack is once you have a solution, it's the same for every other 20b fd you do - and you stand to make a bit of money selling kits.



Mark

I can't imagine why you would want to hamper turn-in and steering feel.



I guess we will just have to agree to disagree. I find it much easier to relocate the drivetrain than to rehang the rack, perhaps your experience is different.

[quote name='heretic' date='Mar 31 2005, 02:57 AM']I can't imagine why you would want to hamper turn-in and steering feel.



I guess we will just have to agree to disagree. I find it much easier to relocate the drivetrain than to rehang the rack, perhaps your experience is different.


[/quote]

Let's not blow this out of proportion here, we're not even talking about large amounts of anti-Ackermann, which is what you'd want for the average driver to notice the difference anyway. Even if we were, I have seen plenty of race cars with anti-ackermann, so it can't be all that bad for turn in (although I won't argue over steering feel).



To be honest I think we're getting a bit trivial over this, and I actually don't disagree with anything you have said, we don't have 20b's or even rx-7's in Ireland (apart from literally 1 or 2 that have been imported https://www.nopistons.com/forums/pub..._DIR). I'm just always wondered why people put up with bump steer on these cars when as far as I can see the solution is quite simple.



Mark

I dunno what "horrid amounts of Ackemann" means, but anyone who brings up Ackermann in relation to a street car should be shot...



Are you moving the steering rack more than half a foot?

If so, you need better customizing skills. https://www.nopistons.com/forums/pub...IR#>/smile.png





-Ted

There is more than one way to skin a cat and I think not moving the rack forward or the engine backwards would be best............I'll let you see the pics when done!

Doesn't hinson supercars have a solution for the bumpsteer. I know they have a subframe for the 20b but I also thought I saw some hardware to fix the bumpsteer.

Hinson supercars sell adjustaable tie rod ends, but you still will have bumpsteer with these fitted ,just not as much.