I have a 94 RX7 with the following mods:

*Racing beat intake
*3 inch Down pipe
*3 inch pipe with high flow cat
*HKS exhaust
*Rising rate fuel preasure regulator
*Fluidine radiator
*Underdrive pullies

Running stock boost
Using race fuel (when on the track)
Using octane boost
Using 1:3 ratio two stroke oil mixed with fuel

I'm having a new motor installed and the shop is recomending an AEM to protect the car on the track.
They say on the street, I'm fine but on the track the car might develop a lean situation.

My question is......with limited mods and stock boost, won't the stock computer be able to adjust for any conditions I encounter on the track? Put another way, doesn't the factory stock ECU have a working range where it can compensate for different outside temp, humidity, altitude, etc?

It isn't like I have different injectors, huge after market intercooler and pushing 14psi of boost.

I just want it stock and bullet proof reliable.

Thanks for the input

 

Not sure about the ECU but I'd think your next move would be an intercooler upgrade is you're still using the stocker...

 

You need one, when u remove the mid-pipe out. There no more back pressure, even with stock boost. There's a chance ur car can lean out...

 

The intercooler is still stock. Thing is I'm NOT looking to get anymore power. Kinda the opposite, I'm trying to keep it as close to stock HP as possible. I'd prefer to get the factory cats but the precat is $1300.00 and the main cat is $1600.00.


No back preasure or just less back preassure than with the stock 2.5" exhaust?

 

On a side note, does anyone happen to have either or both of the stock cats that came with the car from the factory?

 

Bad advise ^ Your next upgrade should be a computer such as the Power FC. Its fully tunable (track or street) and will assist you for mod after mod after mod. Their not cheap but their a lot cheaper than a new engine.

 

I still have my pre-cat.

 

I've got the main cat, and a stock exhaust, shoot me a PM if you want them. I would advise against the pre-cat though, simply because it situates a LOT of heat in the engine bay, and can clog up, causing major problems, the stock main cat will provide plenty of restriction for keeping the boost down.

So long as you have stock boost, and keep it solid at 10psi, the stock ECU should be fine for you.

If you do decide to go with an upgraded ECU in the future I would recommend an Apexi PFC, it's a good unit, the stock map is good for about 13psi, and it's pretty much the standard for ECU's when it comes to FDs.

 

I can send you an OEM JDM downpipe if you want. Very low hp difference between it and the USDM pre-cat.

 

And in this case being standard isn't a bad thing.

...get the POWER FC....


~Shar

 

No, the stock computer doesn't really adjust. It has a set map that it uses.

For the most part, you can run the mods you have... You need to ensure you are keeping the boost at stock levels. If you can do that, you are fine. An electronic boost controller would be a good idea. Also, even if you don't want to increase your boost levels, an aftermarket intercooler is still a benefit. It will provide your engine cooler air and reduce the effort on your turbos.

 

How do you know you are running stock boost? Do you have a boost gauge? With no boost controller is is highly unlikely that you are running stock boost (10 psi) with those mods.

 

Thanks for all the replies, guys.
I'll send PM's for the various parts as soon as I can.

 

I do indeed have a gauge. It was brought back to stock boost by adding an orfice restrictor in the line. Worked like a charm. Brought it back down. I could use a different restrictor to bring it down more or bring it back to 14psi.

Here's a brief history on the car.

When I bought it 12 years ago it had been modified by (I hate to even open up this can of worms) Carlos Lopez Racing in Florida.
The car had been modded to run 14psi on the completely STOCK ECU. Here's how it was explained to me by Carols. The 'fuel cuts' were moddified and a rising rate preasure regulater was added to protect against a running lean situation. He added a restrictor in the line to bring the boost to 14psi. It had both cats removed and an HKS exhaust. The exhaust was 2.5" NOT mandrel bent so it has some 'kinking' and the rear cat was hollowed out.


At the time I bought it, other mods included:

*Cat back HKS exhaust
*Rising rate fuel preasure regulator by Bell engineering


I put the following mods on it:

*Racing beat intake
*Fluidyne radiator
*Underdrive pullies

With the combined mods and running 14psi of boost, I have run 42 track days with NASA, Viper Days, Cobra Club etc and even did the racing school required for my NASA provisional license.

Then one track day at Willow Springs, it was 105* out and I overheated the motor. And we all know what happens when you overheat a rotary.

THE CAR SAT IN MY GARAGE FOR THE PAST 5 PLUS YEARS (which explains why I haven't been on the forum in so long, lol).

Finally, I saved the $$$$$$$ to have a new motor put in it.
Since I now live in CA, I need to have at least one cat on it to pass CA emissions. So, the shop (an extreemly reputable shop in Canoga Park) has a 3" exhaust with a high flow cat. Problem is, they are recomending I put an aftermarket fuel management system on it which is an additonal $1500.00.
I really really really just want everything back to stock. The boost has been reset to factory stock settings.
If it were cost feasable, I'd by new stock factroy full exhaust including the cats. They are dam expensive.

So my question is, since I ran 14psi on the track on a stock ECU (with the rising rate fuel preasure regulater for protection) shouldn't I be able to do the same thing if the only thing I am adding is a 3" down pipe and high flow main cat? And the boost is back to the stock 10psi.

The shop in Canoga Park is amazed at how the car held together for so long with stock ECU and only the rising rate regulater to protect against 14psi boost.

Hope I explained everything OK. If you've read this far please let me know what you think.

 

I think you dodged a bullet too. Probably the race gas.

Based on your stated use and plans, I really recommend going to the Auxillary Injection section of this forum and reading through Howard Coleman's stickys. Water or water/meth injection should be near the top of your list of mods for reliability. And it's a hell of alot cheaper than race fuel.

 

May also want to re-evaluate your approach to fueling? That's a lot of oil

 

A few things:

Using a RRFPR will work. You need to make sure you have an upgraded fuel pump that can handle the extra load. I would assume your car has one already, but you should check.

Next, the stock IC is not all that efficient at 10 PSI, let alone 14 PSI. I would recommend looking into a replacement.

So going from a 2.5" exhaust to a 3" exhaust will increase the flow. At 10 PSI, it won't be a problem. However, since no one knows what your RRFPR is set to let alone what your A/F are at 14 PSI; we can't predict that it would be safe to increase your exhaust pipe size and still run the car the same.

When you are saying "track", are you meaning a road course like Laguna Seca or a drag strip? People throw the word "track" around here in different ways so just confirming.

 

Maybe I should clarify the ratio. It's 1 ounce of oil to 3 gallons of fuel. I should have said that in my OP.

 

[QUOTE=Sgtblue;10177761]I think you dodged a bullet too. Probably the race gas.

Yep, Tri Point Engineering (the rotary gods here in Southern CA) said it was probabbly the race fuel and the two stroke oil 1:3 ratio that saved it.

 

Thanks for the info. I had a few follow up questions.

Not sure on the upgraded fuel pump but will have it checked out.

If I get a bigger aftermarket intercooler and draw in more/cooler air, won't I also be increasing HP? Wouldn't that add to my potentially running lean? Not something I want to do, since I want to retain stock ECU.

Tri Point installed the (replacement) RRFPR so they did the adjustment. Honestly, that was over 5 years ago. Since it has been so long since I have driven it, I've forgotten a lot of the specs/intricate things to my specifically modded car. Have to look through a lot of old paperwork to refresh my memory.

Yes, to me track is a road course. I've run Lime Rock, Watkins Glenn and Pocanno on the East Coast and WSIR, Button Willow and CA Speedway here on the West Coast.

Thanks for all the input and help guys!

 

the stock ecu adds more fuel for cooler air, you've got an air intake temp sensor (AIT) under the UIM.

here's what I would do:
PFC, but you don't really need it, you can find them for sale used for decent prices. (**** the aem)
dudemanownsanrx7 (or somthing like that) has fast-reacting ait sensors, get one.
bigger rad if you don't already have one.
second oil cooler if you don't already have one

it's a bit more money, but it'll save your ***.
next step would be water/meth injection

edit: this guy
https://www.rx7club.com/members/dudemaaanownsanrx7-26639/

 

Seems like with the few mods I have and running stock boost,the stock ECU will be able to adjust for street and track conditions. I will use race fuel and add two stroke oil to the fuel.

The reason I don't want to go to any aftermarket fuel management system is because I honestly think they are hard to tune, not especially reliable and more complicated and trouble than they are worth.

The car is an R2, so yepers, it has dual oil coolers.

I did do a fluidyne radiator.

A full list of all mods is on my car's website. It's www.allhandsracing.com It also shows hand controls I designed in order to drive a car with a manual transmission (kinda cool).

Thanks again to everyone for their input.

 

It won't be "more" air, but it will be cooler air. Cooler air means better power and less likely to pre-ignite. This also means your turbos will not have to work as hard to produce the boost you are set to run. This will increase the turbo longevity as well as make them more responsive (providing you don't get an IC with long bendy piping).

Some info from Steve Kan when he tracked a fairly stock FD:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/hottest-air-water-temp-track-241815/

You can read that his intake temps were pretty high. Something like a Blitz or Greddy SMIC will definitely provide a little safety without having to make the engine look too non-stock.

 

Thanks for the info and the link.

Post # 19 by CrispyRX7 is the single best explanation I've seen.
I also agree with him that the car has way more power, stock, than 90% of guys who track them can use.
Personally, I've done way more suspension mods and brake mods than engine mods. Ya can't use 3, 4 or 500HP, if ya can't whoa it down and get it through the corner.