racer1

Ok ppl i've searched a lot before starting a new thread, but since i am kinda new on rotary stuff i found some posts with custom valves etc that i didn't understand.

Currently i have HKS J-spec intakes and cat-back 3" exhaust. I want to replace the downpipe and mid pipe and remove the cat completely. You think that's gonna be a good mod? What do i have to do to avoid spikes?

Seldon

I don't own a FD, but based on what i've read you are either gunna need a restrictor plate, or a ported wastegate... (someone tell me if I'm wrong).

However, with just a cat, downpipe, midpipe, and intake I dont think spikes will be a HUGE problem... buy a boost gauge and watch though.
-john

bureau_c

Do NOT lose the cat. You'll regret it. With no upgraded ECU you will run lean, and will be at risk of blowing your motor. Spikes...may be an issue. Probably will be, but more risky will be boost creep. With a wide open exhaust like that, I would expect your wastegate will not be able to flow enough to hold boost steady, and it will creep upward, even if you get a boost controller.

At the very least, with the stock ECU you're going to hit fuel cut based on boost levels higher than expected.

Do the downpipe, cat-back and intake if you want...you should be OK, just watch your boost levels.

jds

Seldon

Is it possible to enlarge your wastegate w/o a port? Can you buy a seperate wastegate (I seem to remember seeing an HKS racing wastegate for the fd)? Because this would seem like a reasonable solution to the problem before an ECU standalone/reprogram is needed.
-john

BigIslandSevens

iTrader: (4)

You can do whatever mods you want to do to the car!!! AS LONG as you keep boost at or under 10 psi!! I built one recently with full open exhaust(HKS DP,3" MP, Apexi GT out the back) I just put in the Profec B spec 2 and am currently tuning it. With it turned off I get a 7-5-7 pattern. I have a close to perfect 10-7-9 with it on in the high mode. Even without the controller The car had a 10-5-8 with very little creep. Long story short keep it at or under 10 psi and your safe. Good luck!!

DaedelGT

Seldon, if you want to get rid of the cat, just put a restrictor plate in the MP. I have yet to see someone do it, but it's not hard. Try one with a 1.5 inch diameter hole, and slowly move up from there if you aren't getting the same boost response.

Seldon

Would a resonance chamber (such as the pettit one) provide enough resistance??

I'll have to get an ECU eventually, might as well start saving now.

A number of people talk about running at 20psi Race. What relability mods need to be done to up the boost that high? Is a much bigger IC necessary? New injectors? Or just an ECU that can allow enough fuel to flow to compensate?
Thanks!
john

DaedelGT

Seldon, for 20 PSI you need a lot of work. Entirely new fuel system (pump(s), rails, injectors), new ECU, bigger intercooler, new turbos, etc, etc. Hell, I know I'm forgetting something. Is it even possible to run upgraded twins at 20 PSI?

Seldon

Wow... ok scratch that... my god. Apparently the average work level on this forum is a lot higher than I first assumed, becuase it doesn't seem that extrodinairy. What type of boost level can you expect to get out of the stock twins?

Zoomspeed

wait on the restrictor plate. Some cars experience creep and some don't.

Get a bleeder valve to help with the spikes, and get a boost controller to keep the boost at a safe level. Then on a WOT run keep a good eye on your boost and if u see it rising still. Then get the restrictor plate. If the boost doesn't creep then dont worry about the plate.

DaedelGT

Wow, some people get by with a full open exhaust with no creep? Lucky bastards.

Seldon

Should I forego the seperate boost controller and just go to a standalone ECU, because I have to go there eventually? The current front-runner is the PowerFC, but I'd really like to hook up my laptop to it (I have one specially designated for the task)... which the PowerFC doesn't seem to support. The Motec M4 looked the best of the bunch, but is more pricey than I can afford. Any ideas? (wow this has changed the thread topic)
-john

DaedelGT

You'll need a boost controller of some kind. The ECU (even aftermarket) do not do good enough a job in most cases.

The PFC can have a laptop with Datalogit hooked up.

BigIslandSevens

iTrader: (4)

Definetly get a boost controller. An added bonus I notice is a smoother and quicker transition to the secondary.Has less drop off than without the controller. It is amazing how no 2 engines/cars will act the same way. Another base model out here with the same mods popped his engine with a good spike to 15 psi!!! Ouch!

Seldon

How much do high quality boost controllers run (I've seen like the $500-$600 range) and who makes the best one? I'm not interested in skimping, because I'd rather have a slower car for now with higher quality parts than have to rebuy all the parts when I get where I'm going (400+rwhp eventually, but thats a loooong way off)
john

DaedelGT

You can go the manual route for the least money, but you'll have to readjust it quite often. However, since you plan on producing around 400 horsepower, a Profec-B would do nicely. Look on ebay.

Check out https://www.rx7club.com/forum/showth...hreadid=203040 for a very recent thread on a manual boost controller.

BigIslandSevens

iTrader: (4)

Well I had a AVCr in my 94 with the power FC ,T 78 single etc... I made 400 at 10psi. The face of the gauge decided to take a **** on me so I can't see or change the settings. It still controlled though. That controller to replace is $$$ and it is a pain in the *** to use in my opinion. The Greddy profec B spec 2 I installed is relativly easy to use and is around 300 bucks I think at the Rx7 store.( i maybe wrong on the price) I am thinking about replacing my AVCR with this unit because of the ease of use. You can still program the ECU with the commander if you have it. I've only heard of people having troubles trying to boost over 25 psi!! That's not in my future. Soo it;s all about your plans and pocket depth!!!

Zoomspeed

Well you can get a mechanical one that works fine for aobut $30. I've been running one of these for about a year or so, but if you want to be able to adjust whenever you want from inside the car then I tihnk the profec B is a good choice. Nice price, simple design, and has seperat hi and low settings. All this for the low low price of 315 from the rx7store.

Zoomspeed

wow thats 3 votes for the profec B already.

Seldon

Okay... The pockets aren't limitless. I haven't bought the choice FD yet, but I'll have about 25k to start with... I'm 17, and own a 1968 Porsche 912 now (fun car, but a complete lack of power with no possible mods)... So the upgrades will be slow in coming. Should the boost controller or the full exhaust and intake come first (and just watch the boost gauge)?
john

DaedelGT

What other mods do you have on the car right now?

racer1

Thnx ppl you've been very helpfull...i will replace only cat-back and dp after all and i hope i'll be fine. The only htink i didn't understand is that your pattern is 10-8-10. What about mine? the car is 2000 Type R and on the stock boost gauge it seems that it goes more than 0.7bar which is 10 psi. Is my pattern different than yours or i already with the cat-back installed i have problems?

DaedelGT

Those have the new factory twins, and y-pipe. I think they have a pound more of boost?