Engines blow at different times, and under different conditions. Most of us try to be safe and play the percentages.

You could try to run 18psi with a stock intercooler. You might even get away with it.....once or twice. You could also limit yourself to 8psi, and be virtually assured of no problems. 12psi is a little more risk with a stock intercooler, but you will most likely be OK for quite a while. 15psi won't last long too long, but you could still do it.... for a little while. Choose the risk level you can live with.

"So tell me PUNK, do you feel lucky".....Dirty Harry

 

With what mods?

STEPHEN

 

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I know that I can't run over 10 psi yet, but that's why I am asking now. So when I get all my new mods put on, I'd have a good idea of what I can safely get away with.

 

This assume the IC has some mass, and was not sized for a weed wacker.

SCC measured 2.6 psi drop across the stock IC at 12 psi, with just bolt ons and M2 ecu. That puts the turbos at 14.6 psi to get you 12. Not good for turbo life in the long run.

 

see sig:

 

ok people, how about if im running a water injection system? Can you tell me if it would be safe to run at 15 psi on the stock intercooler. Any help would be appreciated!

 

15psi on stock IC ?
No water injection would help. I mean, just look at that little stock IC.

Someone said that pushing 12psi on stock IC is actually pushing the turbos at 14.6psi. At 15psi you would only get hot air into intake manifold...

 

exactly what I want to know.

 

15 psi is still 15 psi and hot (out of stock twins efficiency range) when entering that baby IC...

So I'm going to say a simple.....HELL NO I WOULDN'T RUN 15 PSI ON THE STOCK IC UNDER ANY CIRCUMSTANCE!

Read what people are saying...due to the light weight design of the IC, it is not suppose to cool effectively past 10psi (or support something crazy like 15psi), and yes some people get away with 12psi. This is getting outta hand. (sorry to preach, but we are talking about safe, right???)

 

Water injection is generally regarded as an alternative to a proper intercooler, not an addition. Most people will recommend against "relying"on water injection to lower your intake charge temperatures because the system can fail due to clogged nozzles, running out of water, etc. If it fails while you are driving you won't necessarily be aware of it and you will then be at the risk of detonation.

A properly sized and positioned intercooler (i.e high flow rate, low pressure drop, good ambient flow to the intercooler) is the preferred option to lower the temperature of the intake charge because it is a passive device that is always working.

In the case of water injection plus the stock intercooler the water injection may be lowering the temperature of your intake charge, but the stock intercooler is still exerting major pressure on the intake system. If you are measuring 15 PSI boost at the UIM and assuming the stock intercooler represents a 3 psi pressure loss, then your stock turbos have to be producing 18 PSI. Premature failure of the stock turbos due to overheating is an almost certainty at this pressure.

Furthermore, at 15 PSI boost and the increased charge density due to water injection you are way past the limits of the stock ECU and MAP sensor.

Finally with your system you not only need to do something about the stock intercooler but also really need to have an aftermarket MAP sensor and ECU tuned correctly to your mods since you have likely upset the A/F ratio in a major way.

Why in the world are you trying to boost at 15 PSI? Do you realize that with a proper IC, improved intake, improved exhaust, and tuned aftermarket ECU you will get a more dense intake charge and therefore more horsepower at a lower PSI? Of course with these mods your engine will breath much more freely so you should add a boost controller to keep your boost down. This is a much safer way to increase your power output.

 

Well said...I am currently running 10psi with all the mods you listed (*edit* full emissions P/S and A/C) and I am putting 300rwhp @ 6700 rpms.

If you do it right, good power can be achieved (it's not cheap either). ~off soap box~

 

To me, there is no real argument here.

The people that are running more than 10 psi on their stock IC are thinking they are getting away with something.....they're not. They are paying with higher intake temps (more wear on motor) and increased turbo wear.

The only reason not to upgrade the IC is because people don't want to do things the right way -- they want the power without paying to make it RELIABLE. The longer I own this car, the more apparent to me how true the phrase "you got to pay to play" is, if you want a fast AND reliable car.

Just my 2 cents.

BTW, my mechanic just did an engine rebuild for someone running 15 psi through the stock IC -- engine blew because of really high intake temps....

 

Alright, thanks everybody. I'll just keep them at 10 until I can afford a good FMIC. Appreciate the advice.

 

I don't drive it with my foot in it so I'm over 10 psi all the time. Probably why it's lasted this long. I'm not really worried about it. It doesn't run 14 psi except when it's cool which compensates for the higher boost temp. In warmer weather it tends to bleed back down to 10 psi by itself. I am also careful to stay out of the boost until the car is warmed up. If it dies, it dies and I'll just get a new motor spec'd out the way I want it. I believe my FD had a new reman just before I bought it...

 

I'm running .85 bar on stock IC.. I used to have PFS IC.. but my damn new hood didn't close with it, so I sold it.. Yesterday, I have put my Greddy 2row FMIC..

Anyhow, that's about 12psi on Stock IC.. But my PFC is tune rich..
I do understand about the increase in heat temp due to small core.... but I don't understand why that would cause detonation.. as I am not 100% how things work.. and please correct me if i'm wrong.. but doesn't increase in heat makes air molecules more spaced apart in turn less air into the system.... so, if you ran same psi and one IC with lot lower temp, I would think that will increase the chance of detonation than one with higher temp??
Just wondering if this is correct or if I'm completely wrong please state your reason....

 

I'm running .85 bar on stock IC.. I used to have PFS IC.. but my damn new hood didn't close with it, so I sold it.. Yesterday, I have put my Greddy 2row FMIC..

Anyhow, that's about 12psi on Stock IC.. But my PFC is tune rich..
I do understand about the increase in heat temp due to small core.... but I don't understand why that would cause detonation.. as I am not 100% how things work.. and please correct me if i'm wrong.. but doesn't increase in heat makes air molecules more spaced apart in turn less air into the system.... so, if you ran same psi and one IC with lot lower temp, I would think that will increase the chance of detonation than one with higher temp??
Just wondering if this is correct or if I'm completely wrong please state your reason....

 

Don't make this more complicated than it is. Here's the rule of thumb:

The higher the intake charge temperature, then the higher the risk of detonation.

 

I believe the stock IC is good for at least 11 psi.

I understand that the stock IC is used in all RX7's including the latest J spec models. Those Japanese cars run 280 Hp because they have a freer exhaust and upgraded turbos, which means they run higher boost than US stock cars. I think they run 11 psi.

 

Sorry, but that's a ****-poor argument. Anyone who has monitored intake temps and upgraded to an aftermarket IC and seen the reduced pressure drop will tell you that.

BTW, Mazda still used a plastic AST tank up until the end too. Still want to argue the point?

 

the stock intercooler sucks in the first place and should be replaced. just look at the size of it compared to even the smallest aftermarket I/C. This thread is a given, replace the I/C right away, you have already spent the money on everything else you might as well finish the project. Not buying a bigger intercooler and doing the other mods is like making a peanut butter and jelly sandwhich and not putting on the peanut butter, its just not complete, get the picture... its for your own good. Spend the money....

 

Rynberg:

Not sure what you mean about arguing a point. I don't think you have argued anything. I agree with you that that a better intercooler is better. Pretty hard to think otherwise.

My point that if Mazda is selling cars running at 11 psi with a US spec intercooler then their engineers must believe it is capable of performing OK during the life of the car and therefore we, in the US, are probably OK running 11 psi without major headaches.

Now, if anyone has data that says the reliability of the 280 HP engines is poorer than US models then maybe we can argue.

 

Salamander,

I would say that your comparison of the operation of cars in Japan to those in the US is dangerously shortsighted and incomplete because you fail to account for all of the differences.

My understanding is that the octane rating of gasoline in Japan is much higher (103?). Higher octane gasoline helps guard against detonation. Also, my understanding is that Japanese RX7s have different tuning programmed into their ECU's. A richer A/F ratio helps guard against detonation. There are likely many other differences that I am not aware of, but just these two factors alone suggest that you may "get away" with operating a stock Japanese spec vehicle at a higher boost.

If you can't present a complete unbiased explanation of the differences between Janpanese and US RX7s and how they are equipped and tuned then I suggest you refrain from offering advice that could lead people to unreliably operate their cars!

 

The 103 in Japan is call 103RON not octane and I THINK its equates out to 95octane or something like that.

Anyway, personally I think its fine to run over stock boost with the stock IC, I did it for years with no problems. The only real issue to me is the pressure drop, if your running 13psi on the manifold your turbos are prob running about 16psi in reality which heats the air more.

Going back to what I said earlier, if you have a PFC (which the original poster will) just watch your air intake temps, dont run high boost if they are over 50C. I see absolutly nothing wrong with running 12psi all the time with the stock IC. When it was real cold outside I even had mine up to 13-14psi.

just my .02
STEPHEN

 

That's not reasonable. No one on this forum could provide what you are asking for.

I personally believe the stock intercooler will be fine at 11-12 psi. M2 sets up their ecu to run up to 12 psi with a stock intercooler. Don't ask me to provide every possible explanation for my OPINION. I can't, and neither can anyone else.

 

How about some intake and ambient temperature examples?

I'm not sure how accurate the Power FC intake temperature reading is, or were it collects the temperature data, but just cruising around here in Scottsdale, Arizona yesterday, and after a couple long red lights, without even pushing boost, I saw 75C(167F) for an intake temperature after about a half hour of casual driving. At that time during the day it was 40.5C(105F) ambient temperature . I'm running 96 octane fuel with stock IC, DP, CB, PFC and stock turbo configuration. I don't believe it would be wise to be regularly boosting at all given these conditions. 12, 13,....15lbs bye, bye engine.