So I am planning on one day going FI. I have been through so many build threads. So many different approaches to the same idea. Before some one suggests getting a different car know I begged my wife for the 8 for years. I want to make my 8 a little more efficient and a lot more fun.
I like the change in gearing for the 5 speed vs the 6. For the time I think that would be better then the 3.45 Camaro diff from https://keislerautomation.com/products/mazda-rx8-5th-gen-camaro-differential-installation-kit I dont have the power for a 52 mph first gear. With the 5 speed 70 mph will be right about 3k rpm. That might give me some of the efficiency. Anyone with experience with this please tell me how far off base I am.
I have been thinking of getting a flash tune program. I dont know versatuner or mazda edit. I have started down this path already. I bought a laptop for this alone. I just dont know what to go with.
if my wife will give me the go ahead in feburary and I can get a used pettit sc. I would like to go that route. I would like to not have the pressure spike between the exhaust ports and turbo. This is the area that all the build threads I have been reading has made my head

thank you guy for taking the time to read through. Where I am off base let me know dont treat me like the childre nbn that dont listen and do what they want. I dont want to build rebuild new components over and over.

 

You're going to have to make a decision whether you want more horsepower or better MPG. Putting longer gears in it and a supercharger will not give you better mileage. If it were that simple, Mazda would have done it from the factory.

The general consensus is that Mazda runs the car purposefully rich to keep the cat pipe from failing. So removing the cat pipe and pulling some fuel out of the fuel map via Versa or ME is really the only way to increase MPG. By time you buy either one of those fuel management programs, install a mid-pipe, and tune it, you will be $1,000 poorer.... Is it really worth a grand to save a few bucks per fill-up? Are you really going to have the car long enough to ever recoup that money?

Now if you want to go forced induction, your MPG is going to suffer severely. I literally only drive my car to and from the gas station....

 

pettit kits are no longer made and very expensive. my buddy has a s/c and his mileage sucks

 

I will express the idea with a joke:

You know how Ford now has a line of Ecoboost vehicles?

Clearly, they forgot a slash somewhere, because it should really be Eco/Boost.

A supercharger won't increase fuel economy, ever. The whole idea is that it leeches off some of the engine power to compress the intake air. You will lose efficiency.

A turbocharger can, but as I mentioned, it's Eco/Boost. I talked to a guy with FD RX-7 and he told me that he can get relatively good gas mileage by tuning it a bit leaner, but the car does pretty much nothing when he puts his foot down. Want power? Gotta run pig rich or the engine knocks and eats itself.

According to Brettus, running leaner doesn't help much.

https://www.rx8club.com/rx-8-discuss...4/#post4871665

And even without the cat, there are some other components to worry about. You still have the AFR sensor and you don't want to toast that.

 

Thanks guys. I guess mpg will be out the window.
I know the petits have been discontinued for some time. Only reason I put that in was I found 2 in the FS part of the forums.
I was tempted by the idea of the hybrid msp/gse 13b. I found out that without reengineering the irons it's pointless.
I guess the answer is turbo. I guess with that direction a good piggyback is the best way to go. I have looked at the esmeril turbo v3 kit. Not the hp variant.
it is tempting to get a spare msp. That I have a half approval for already from my wife.
Will I have my 8 long enough to recover the $ I invest into it. Simple answer is I do not want to jinx myself.

 

The fact that you are already talking "approval from my wife" spells it out pretty clearly from where i'm sitting . A turbo or SC is not going to be a good thing for you . Forget it and go buy a faster car.

 

That is not what I want. I have had the rotory bug for years before I could even drive. I'll never forget riding the school buss and seeing a brand new black rx7 back in 94. I have attempted to steer away from the rotary and listen to my step father. I couldn't I love my 8. Now i am wanting more out of it. Out side of normal bills in my house if it's more then $500 we both get approval from each other. Just how we keep from fighting over $. When it comes to me and a car with the $ she has no problem till I say anything about making it faster. 1am aug 4 2004 I got pulled doing 113 in a 35. I got away with a slap on the wrist. My wife thinks that's me anytime I drive alone.
please don't say get a faster car. I know I want my 8 faster. I just have not figured how I want to do that yet. Brettus I have enjoyed your build thread. I admire the work you have put In. Thank you.

 

turbo is gonna be cheaper than a s/c kit but you are still looking at 10k to do it right and that doesnt include a rebuild. either will gain you about 100-120whp. you could go n02 its cheap and easy. i ran it for years as did many here. my buddy has my old kit and is looking to sell it because he went turbo

 

I appreciate the suggestion. Nos scares the **** out of me. I dont know if I could get past the panic with the bottle in The car. I have been hit by shrapnel in the past.

 

i tagged a big deer doing 85mph with a bottle in my trunk. granted it was hit with the front of my car but i never worried about the bottle blowing up

 

I don't really understand what you want from us but would say ...from what you have said so far, you are probably correct in that the lowest risk FI solution is the Pettit kit . There are a few around now so be in quick cuz I guarantee there wont be one available when it suits you.

 

It maybe an irrational fear but it is what it is.

 

I think Brettus is just saying that if you are on a tight budget or have a budget restriction, then you either wait until you have the cash saved or you go for an old Mustang or something.

There are only so many corners you can cut.

Interestingly, I have someone(that same FD RX-7 guy) who has been talking to me about it recently. Is it really 10k? He was saying closer to 20k but IDK how updated his knowledge is since he lives in New Zealand.

 

a proper f/i build isnt gonna be cheap, trying to cut corners will cost you an engine. theres no cheap hp in the rx8 game. i had manifold back exhaust, pulleys, intake, tune etc and put down just shy of 200whp on a dynojet. about 230 with a 55 shot of n02

 

When I say "cutting corners", I realize there aren't many you can cut. Definitely not on the engine. The dude just told me you can pick a turbo and intercooler with better value, etc. But even then, he made sure to get the same point across: it won't be cheap.

 

Thanks Brettus. I have an idea of what I want up to the engine and trans. Once i get to that point i just seem to get stuck. Like a little kid in a candy store that's never had candy. I like the idea of FI I dont want to go overboard though. I think getting 300 to 350 whp would be just about perfect. What's the easiest and safest way. I think I just need help picking the right path to get to my goal area in power. I also have never driven a turbocharged car. I dont know what to expect going that route. I need to get the books recommended in the dummies guide to fi thread. I know my wife will be ok with spending the cash for one direction. If I go sc or turbo that's what I will have. I want to make the best choice.

 

thank you. I know rotary market is a small % of the market. Higher prices all around. I am good with that. I am fond of quality parts and tuning. I do cnc work for a living.

 

Ok so I have a lot to learn. I'll still keep my eyes on the pettit kits but I am going to study more. February is when I am expecting to start down the FI path. I am going to grasp the fuel lbs and air lbs per minute better. Thanks to all that has been helping. I am sure I'll be picking at yalls brains some more. For now any documents that have helped your knowledge base with any FI type I would gladly read through them. I still have to find some of the books from the dummies thread.

Brettus I enjoy your Mazda edit thread and the build thread. I will get a better understanding of all you numbers and charts.

Jin thanks for the advice in this thread and over in the new members side.

200 thank you too. I will not be running NO2 anytime soon.

 

If you go turbo, the two easiest ways I can see are a second hand Greddy kit, or an rx8performance kit.

 

I agree that these are great kits ............. the supplier , not such a good rep. unfortunately . I would advise anyone wanting one to avoid paying up front.

 

Thanks if I go turbo I may build the manifold myself. I need to weld some more. I am also thinking when I start the build of going with a fuel delivery system that will accommodate e85. Mainly for the detonation reduction and cooling benefits.

if I do the fuel system for e85 for a max of 500ish hp. I dont plan on pushing that hard I just want the over head. Will that hinder running a gas tune for 340 ish hp when I go on a road trip.

I am keeping turbo as a most likely way to go. Being Feb is my time frame for spending the $ on it. I am not holding my breath for a pettit supercharger to be available then. Has anyone run the Garrett g25-660 or 550? I have been attempting to get a preliminary draft of a turbo setup going in fusion 360.

thanks again. Good night.

 

First time I've ever heard of those two . The 660 has enough compressor flow but the turbine is too small for a 13b rotary ...........IMO.

 

I will take your opinion. With all the reading of your posts Brettus I know you know your stuff.

 

Well I am going to be getting a replacement renni I plane to get it built for going FI so I don't have to do it twice. I have not made up my mind who I'll get to do my build. Any suggestions I'll look into them. My top 2 are defined and rotary engine. Com. I shed a few tears today. But the few min of morning my engine quickly became excitement for a new build.