If i were to install a new and bigger intercooler into a stock 3rd gen rx7, would that resolve many of the problems that are found in the 3rd gen rx7s? If so: which one?

 

No it does to resolve any problems...

It cool the intake charge air ...making you have a potential new problem...IE lack of proper fuel with your new air

Please tell us what problem you are trying to solve

 

It makes problems like a highend miss because the stock FD ignition sucks! I should have a SMIC apexi unit sooon

 

no real problem, but thats what i heard from some other board. The guy said that an biger intercooler would be needed if you try add any mods to the rx7, since it would overheat and stuff.

 

intercooler cause high-end missing???? intercooler on stock boost levels just lowers intaek temps. Furthermore, it does not cause lean condition because ECU just compensates for colder air coming in. AT high boost levels intercooler is needed to keep up with increased heat from turbos and psi.

 

what's wrong with the stock ignition?

 

The answer is: BOTH. It helps solve some problems (lowers intake temperature, therefore reducing chance of detonation), but it creates problems by the same method -- lower intake temperature means denser air which needs more fuel, so you're more prone to running lean and having boost spikes ... so you need to compensate for these issues. Get it? What that guy should've said about the "overheat and stuff" is that you need a bigger radiator, which is what keeps the motor itself cool. DK said "Koyo".

 

smic apex? are you custom building one w/ an apex core or something? i've never heard of an apex smic...

 

As far as running lean goes, a good IC upgrade does two things:

- Lowers intake temp, which the stock ECU should account for properly. Intake temp affects density, which is accounted for in a "speed-density" injection system like the FD uses.

- Reduces pressure drop in the IC. That means the turbos don't need to make as much boost to achieve the same manifold boost pressure. Since the turbos do less work, they offer less restriction in the exhaust system -- less backpressure. Less backpressure leads to greater flow at a given boost pressure. The ECU cannot account for this because it does not measure flow. This can make you run lean.

With the stock ECU and main cat, a downpipe, cat-back, intake, and M2 Medium IC, my car would detonate big at 11-12 psi. I ran it like this only for a short time while I drove down to MADS to pick up my ECU upgrade. I don't think it would have detonated like that without the IC.

-Max

 

A few questions:

I plan to finally upgrade to an M2 stage 3, (airbox and M2 large with battery relocation), WITHOUT the M2 ECU upgrade. Reasoning is that I don't plan to run higher than 10 psi boost, so why not use the factory ECU? I want the bigger IC is for maintaining cooler air charge temps during the summer track events to reduce the chance of detonation.

Currently, I have a downpipe, high-flow cat, and catback, with RB intake duct and K&N. The boost is restricted to 10.5 psi spikes with a wastegate pill with a slightly larger-than-stock diameter orifice.

Knowing the mods I have on the car now, AND that I plan to replace the stock airbox/RB duct and stock IC with the M2 Large IC, and airbox, do you think I could restrict the boost with an even larger diameter restrictor pill--to compensate for the reduced drag on the turbos, thus decreasing back pressure in the exhaust--and remain safe from lean conditions or detonation?

Also, do you know if the M2 Large IC plumbing will fit UNDER the R1/R2 strut brace? Every pic I see of an M2 Large IC and its associated plumbing, I see the Cusco strut brace, NOT the factory R1/R2 strut brace (I have an R1). IMO I think the factory brace is so cool with the "Rx7" logo right on it. I'd hate to replace the factory brace with the Cusco. I guess if I had to remove the brace altogether to allow the M2 IC plumbing to fit, that might help with my increased understeer problem with the staggered fr/rr tire setup?

Thanks in advance!

 

You dont need a upgraded IC with the stock ecu. The stock ecu only supplies enough fuel for 10-11psi of boost and at those boost levels the stock IC is just fine. If you plan on running stock boost for now but want to help the intake temps some get a good intake and mount a fan on the back of your stock IC so it doesnt heat soak as bad at redlights and such. You dont need a new IC unless you running 13psi or higher. The $ you'd spend for a IC would be much better spent on other things depending on what you already have. You would be better off doing intake, exhaust mods, ecu upgrade, cooling fan mod, vac hose job before a IC.

my .02

Later,
STEPHEN

 

The stock IC has high pressure drop, and is essentially useless at the track, where SCC measure 248F after it at 12 psi. The M2 large read 158F. 85 deg test day.

The stock ecu likely has a biased temp correction, ie more than density based fueling when things get hot in the manifold. With other mods that nibble at the overrich margin, the real big IC's can lean out and result in oem ecu knock, esp in cool/cold weather. Mid pipes can be trouble too.

For road events, the big stock mount performance is limited by ducted air. I'd suggest the improved pettit or greddy mid size IC's for u. Huge improvement over stock. The very heavy, big sm's still have advantage at the drags/auto-x, if precooled.

Dyno to be sure on fuel ratio, esp in cool weather. For a modest bump in richness, a simple $100 RRFPR can be added for up to 10% more fuel, using stock ecu. can be tweaked some too.

to original, post, IC upgrade is not a universal fix of any kind.

 

This reads like an excellent answer to my post, but I'm afraid I'm not getting it...

So the M2 large IC decreased charge air temps 100 degrees at 12 psi (not 10 psi which is what I plan to run). That's good for horsepower, but how does a cooler, denser air charge protect against detonation or lean fuel mixture, if I only plan to run 10 psi. It seems to me that I'd detonate at 12 psi with the stock ECU, IC, and intake?

In my case, I want to protect the motor from damage, while at least making consistent, as advertised "stock" horsepower during a warm day on a crooked track. Hence the idea of 10 psi boost restriction and larger IC for cooler air charge (for consistent horsepower production).

So how can the large M2 IC lean out the fuel mixture, if I'm restricting my boost to 10 psi with a larger orifice diameter wastegate pill?

I have 3-inch diameter exhaust tubing throughout... downpipe, high-flow cat (which amounts to a midpipe with resonator pack) and Trust catback.

Didn't get the last sentence of your response. I don't understand the abbreviations

P.S. I'm interested in the M2 Large IC because it's the same price as the M2 Medium IC; and I eventually want to relocate the battery to the back for better corner balance. That's 40 lbs of lead-acid battery sitting in the left front corner! Hell even BMW moves their batteries into the trunk for better weight distribution. What the hell was Mazda thinking

 

Ok, let me rephrase my question. I have a completely STOCK 93 RX7. I plan on adding things such as new intake, exaust system, and all those starting modds. From what I have heard, adding these mods can be dangerous if you do not have a better intrercooler then the stock IC. I need to know this because if i install these mods, and then f**k my car up, i will be in some deep crap.

Should i just add these mods and forget about the IC? Or should i get the mods, and before adding too many, then get a IC? Or should I get the IC before adding anything?

 

You're asking what the chronology (timing) of the modifications should be for your FD.

Visit these sites:

http://www.rx7turboturbo.com/robrobinette/

http://www.scuderiaciriani.com/rx7/

 

the site you gave me is very good, however it is too general, since it is not rx7 specific. The rx7, to the best of my knowledge, does not have a good stock IC. So, before you can even start some of these other modifications, you need to add a better IC. That is why i am asking if this statement is correct or not.

 

what're u talkin about? those sites are exactly rx7 specific. look at the freakin domain names, rx7turboturbo.com and scuderiaciriani.com/rx7/... that would sorta indicate they have something to do with rx7s. but to answer your question, no you don't need an ic first. to make it simple, you can go dp, cp, intake before getting an ic and you might actually want an ecu before the ic.

anyone else think we should have maybe a 3rd gen newbie section? it would sorta group similar questions like these in the same area so it wouldn't have to be answered over and over again.

 

calm down man, i didnt notice that. no need to get all ticked off.

 

so obviously you didn't bother to read what's on those sites if didn't notice that, when you click on either of those links you immediately see pics of rx7s, yet you said it's too general... nothing personal, it's just irritating after a while when new users keep asking the same questions without actually doing any research.

i guess i'm sorta being a dick but oh well... it's irritating.

 

I had initially posted AIM's site. I then realized they cater to more than just Rx7s, and edited the post to reflect the Rx7-specific sites.

Omayre must have read the inital post before I had a chance to edit it with Rob Robinette's and Steve Cirian's site.

Sorry about that guys!

FWIW it is sorta irritating to see the same questions and posts over, and over again.

But it's that way with any hobby. The veterans are always training the novices.

To answer Omayre's question...and this is strictly my opinion.

I would start with the exhaust and intake first. This is the most cost-effective way to make horsepower, and fairly safe. The main cat and precat provide enough exhaust back pressure to keep boost spikes beyond 11 psi from occurring (very bad).

Once you're ready to replace the catalysts with open pipes or high-flow cat, do the ECU and intercooler. These in conjunction with the intake and exhaust will make even bigger horsepower, assuming you're turning up the boost, and your ECU is adding appropriate fuel to the combustion mixture.

Be careful to limit your boost to a conservative level...with an ECU upgrade, no more than 12 psi tops. This is for reliability's sake. If you're dragster, or don't mind replacing motors every 10,000 miles, then go ahead and turn up the boost to 15. It's your wallet

If you're a crooked track racer (like I am), then for God's sake don't run anymore than stock 10 psi boost levels. These motors run very hot compared with their piston counterparts. On a crooked track your motor revs between 3000 and 6000 rpm for 20 minutes at a time for 5 sessions during the day. The higher the revs, the more boost you pump in the motor, the hotter the motor runs, and the shorter the motor's lifespan will be. And if you turn the boost up to 12 or 15 psi on the crooked track while turning these rev ranges? Forget it. You will take your FD home on a trailer. Those boost levels are strictly for the 12-second straight track racers!

I've been running my car at stock boost levels and the stock ECU with RB duct, K&N filter, downpipe, high-flow cat, catback on crooked tracks for 5 years. My R1 has 92,000 miles on the original motor and turbos. The key is the 10.5 psi boost restrictor pill I use in the wastegate. It's slightly larger in diameter than the stock pill, which allows more boost to bleed off thus keeping the boost well within the stock ECU's operating range.

Generally 11 psi for short durations is ok with the stock ECU; so staying under that boost level is critical for motor reliability's sake.

Read Rob Robinette's and Steve Cirian's sites. They're both very good.

 

i see... i apologize for my comments to omayre then. i didn't realize the link posted may have been to a different link before. i still think it may be useful to have a new sections tho.

 

As max said, lots of mods tend to lean out the mix, even at 10 psi. u have proved you can do intake and exhaust, with orig ecu. But a big efficient IC with low pressure drop could put u over the edge, esp in cold weather

The big IC reduces max pressure drop (by 1.5 psi at 12 psi boost) and results in less exh back pressure (1.5+ psi at 12 psi boost) at a given boost and rpm , like 10 psi and 6K. This is more air that ecu does not know about. It also will be lots cooler at 10 psi ... denser air for even more power at 10 psi. But, my opinion is stock ecu has super rich maps when high manifold temps occur to cool things off and compensate for no real IC ... like water injection at high boost and no IC. Brian at M2 also thinks this is true. The BIG IC's will drop you out of the super rich maps, even at 10 psi.

I have run same mods as you with the Greddy stock mount IC with no knock. I think max, year or 2 ago, said that he heard knock with these mods at 10 psi on a cold day, stock ecu. Others reported problems with mid-pipe and other mods, stock ecu.

I use a 51R pep-boys civic sized battery, about 24 lbs. I used to have a mod'd oem tray, but now have a custom alum one. Could get a group buy on them for about $70 ea. Rad breathes better. Big M2 would still not fit.

The RRFPR is a rising rate fuel regulator.

 

haha, yah that is what happened. cause i bookmarked the site and it is AIMs site. lol. Hey i forgive yah man. And Sleep, thx for ur opinion and great links!

 

Let me check for understanding...

So even if my boost restrictor pill is set to control at 10 psi, you and Max are saying that the stock ECU will not detect the 1.5 psi pressure drop that the M2 Large IC provides the turbos, which is in essense, is 11.5 psi of real boost, not 10 psi. At a 10 psi read out on the boost gauge, I could actually be causing a lean condition due to the decreased back pressure and denser charge air at the nominal 10 psi boost restriciton...is that right?

I'm still not clear on the back pressure thing from the decrease pressure drop that results from a large IC. If backpressure decreases (whether by removing catalysts, or decreasing pressure drop aft of the turbos), the turbos, presumably, will make more boost pressure in the manifold, and the gauge reading will also increase accordingly. The boost gauge read out should be what the actual manifold pressure is; the boost gauge won't underestimate the actual boost pressure by 1.5 psi, right?

I do get that the cooler denser charge air may not be compensated for by the stock ECU. So in that instance, if the manifold pressure is reading 10 psi of cooler denser air charge, then more fuel would need to be injected into the combustion chamber to avoid a lean condition. I guess this all depends on how our stock FD ECUs measure air and fuel. Is it density, flow, or temperature?

If the stock ECU measures manifold air temperatures, then I can see how the ECU would run rich when using a stock IC at the crooked tracks.

If the stock ECU measures manifold air flow, then the stock ECU would still be ok, IF you limited boost to 10 psi (manifold pressure is a reflection of exhaust AND intake flow speeds), presumably.

If the stock ECU measures air density, and the ECU DOES have a maximum air charge capacity, then I would be in trouble with the stock ECU. I wouldn't have any way to know what that air charge density maximum is with my current gauges (boost only). Even with an air-fuel meter, you wouldn't have much time lift off of the gas, if you suddenly saw the lights go into the yellow/red zone, even though my boost gauge is reading only 10 psi. This is the scenario you Max are painting with your posts, right?

If that's true, then there is no safe way around the lean condition issue without considering an ECU upgrade.

The next BIG QUESTION IS:

Will M2's ECU Stage 3 upgrade support my high-flow catalytic converter, instead of the main cat converter that they encourage FD owners to use. I've just read that the M2 ECU Stage 3s cannot support midpipes. If you look at my Bonez Hi-flo cat, you'll see that it's basically a midpipe with a small catalyst pack inline of the exhaust flow.

 

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