It doesn't if you move the 20b back. That's been been done time and time again. If done correctly you will have an even lower CG and polar moment with more weight towards the center of the car. This is something you can't do with the LS1 unless you completely trash the fire wall.

 

Something to consider. Going NA will save a ton of money in the beginning stages as the engine can always be turbo charged at a later date.

 

jjshaloam just weighed his and it came in at 2,811 lbs. with 1/2 tank of gas. It was also pretty balanced across the 4 wheels:

https://www.rx7club.com/20b-forum-95/20b-fd-weight-819232/

I'll take this any day.

 

Just to give you an idea of weight:

I have an R1 model with AC/PS a 20B and a single turbo GTK 850 BB on a stock sub frame about 2 inches from the firewall ( no modification on the firewall) No CF parts with a full tank and me inside of it (185LBS), full interior, battery relocated to the trunk stock R1 shock with Eibach springs and the car weighted at 1400 kG * 2.2 = 3080 LBS with 51/49 weight distribution.

I hope it helps

Andrew

 

How many lbs do you want Andrew?

 

Canadians weight less right? That puts the actual weight of the car right at what jjshaloam found also and I'll take 2,800 lbs. and that amount of HP any day.

 

Wow what an awesome typo I made. I would put Andrew around 180lbs. Yeah thats not much more added weight I guess or at the very least its worth it. Very true David.

 

Im hoping my N/A 20B with A/C and P/S delete, 1 piece forged wheels, CF seats and some other slight weight reductions would come in at somewhere around 2600lbs. Honestly Im hoping for just a bit over 2500 but dont want to set my hopes too high

 

Not sure who that comment was directed towards, but if youve seen some of my plans from years ago, youll see that I had planned on going LSx for a while myself. Thats why I have the cobra 8.8 setup in my car, and I had a LS1 subframe. I just decided that I myself would be happier with a rotary. I have no problem with LS1 swaps at all, although too I really hate to see them in the rarer models, such as a CYM or spirit R, etc. But I would feel almost the same about a 20B.

 

You could... but if you were building an NA, wouldn't you use higher compression rotors such as S5 NA? Forgive my 20B ignorance. If so, this would create problems when boosting later with total power, & limits with pump....

I honestly really do see the OP's point of view on this. A 375hp FD is plenty fun. With the torque, reliability, and simplicity of an NA engine, it would be nothing but bliss.... However, for me, the first time I got smoked by a FD with a single, I would be planning for a turbo build. It's a 20B....

Maybe my ego is too big, or my ego for my FD...LOL.. and I should take it out of the picture. But with ALL the work, money & sheer effort involved in this swap.... I would want it to simply dominate everything. I would never go through the process with a product that I wished was a little faster. I would want it to always surprise me.....

Again, just my opinion. I think the OP is going to end up with a GREAT car, and I totally agree with others.... DO IT!!!

 

i hope to one day start my 20B but personally i cant seeing going N/A as an option sure i could make 350+WHP but honestly i could do that with my 13B im actually making more now. if im spending the money i want the power maybe not a massive turbo, like the supra boys are running but a large single. if im going to build it its going to be an all out make power build or bust deal. im not looking for a 900RWHP FD that is just stupid on the streets. but maybe in the 650-700 range. sure that is a ton of power but the car will be built around the engine, as i see many 20B builds going lately.

 

This is like taking a 1.6L turbocharged motor out and putting in a 2L vtec (s2k) engine in. Fun for a while but you'll be craving boost sooner or later

 

Its actually a bit more like taking a 1.3L turbocharged engine out and putting a 2.0L engine in.. but whos checking

 

Well, in piston engine terms it's like taking a turbocharged 2.6L out and putting in a 3.5 V6 j/k eitherway good luck with the conversion.

 

Not quite true; Mazda had initial plans in the FD's development for a future 20B version.

If you are going to do a conversion worthy of the car, you cannot take short cuts, you can do it and get both OEM fit and finish along with tremendous performance. Whoever in this thread said you can go N/A and save the money of turbocharging is very mistaken on the logic to that the 20B road. Whether you go N/A or turbocharged should be a matter of personnel preference not a $$ saving opportunity, any savings if any, would be mere round-off. I have not started down this path because I know I will not accept any short cuts and I am not yet ready to make another 50K plus financial commitment to the car.

 

this is true the FD was started in the stages of coming with a 20B but they said it weighed to much and the idea was scrapped. but man do i wish they shipped them here with 20B's. would have be a damn super car for the day.

 

Like many others have said, especially the words from Mr. Clark; Do it, if you can afford to do it right.

 

i agree 110%

 

You could use either rotors. Also the limits are all in the tuning when it comes to boost and compression ratio. Because of it's larger displacement, 20b needs less boost to create the same power than the 13b. There are plenty of 20b's out their making 600 rwhp on 93 octane alone (no water injection, e85 ect). Also if using 9.7 compression rotors, you will make the engine (13b or 20b) more responsive and make more power with less boost. streldoc on this forum is a perfect example. He has a 9.7 compression 20b fd with gt40r turbo and making some crazy low rpm power. Here's his 11psi dyno graph:

http://www.7parts.com/forums/viewtopic.php?t=12

When was the last time you ever saw any rotary make that much torque that low in the rpm range? It's very v8 like but not rev challanged like a v8. It's reasons like this that makes 20b swap worth the money because your making soooooo much usable power and not stressing the engine at all. Less stress makes it far more relaible in the long run.

Hi compession is nice however, you will reach knock levels sooner with the increased pressure ratio so you have to have it tuned really well. There's always a side effect. You just have to have an understanding of the side effects to have a relaible set-up.

 

The FD might still be in production if they would have gone n/a 20B. Would have solved alot of headaches.

 

^ Exactly!

 

I'm not quite sure high compression + boost is a good idea. The rotary already has an issue of knocking a couple of times and needing rebuilt. Would you really want to run an engine even closer to that knock threshold than normal? I wouldnt, especially if I had 3 rotors to redo

 

I think it would have been THE supercar of the day. It was damn close to being a supercar to begin with. If only the car were a little more heavy duty it would have been perfect...but that means more weight. give and take I guess.

 

a 20B in any car . especially an FD ... is like marrying a 25yr old and yur 75 .... just makes sense .... it`s a no brainer ... if u can afford it ... everyone will envy you .. yu lucky sob

 

As I said before, if all comes down to proper tuning.