I currently own a Acura Integra (too slow) and a CBR600F3 (not slow, but too much trouble with police). After Sep. 11, I enlisted with the US Marine Corps, so I can go shoot some MF's. When I get out of basic, I am planning on selling both the acura and the bike, and then with a loan from uncle sam, to get a 3rd gen twin turbo. I have decided that while living on base it will be easier to own just one vehicle, so the bike must go. Now, with the new RX-7, I plan on making as much HP as possible, including the installation of a single turbo. So anyway, now that you are bored and know the situation, these are my questions:
1. Assuming that things like fuel and timing are modified, how much psi can the stock engine components safely handle?
2. And becuase I know nothing about rotary engines, what type of engine mods would be the equivalent of adding stronger pistons, rods, etc., for strength or performance reasons?

Thanks for any help

 

i'm not an expert but i'll take a shot at helping you out. i believe stock the boost pattern should be 10-8-10. if you decide to turn the boost up most people on here say 12 is the most you should safely run, and once you upgrade the fuel pump and injectors 14 is no prob. you can run 14 totally stock but at that point the fuel pump is maxed out and you fun the risk of running lean, so until you upgrade don't go over 12. as far as making the engine stronger i think a street port would help because it'll help the engine run cooler as well as all the basic safety mods (dp, fan mod, better radiator) will help too. The engine isn't a weak engine it's just real finicky. ok well hope this helps...good luck

 

No you didn't say pistons ......Lesson #1. 3rd gens are powered by a Twin Turbo 1.3 liter 13Brew ROTARY ENGINE

 

Try reading it again before you jump all over him.

He said, the EQUIVALENT of adding stronger pistons. He knows it's a rotary...

 

The "EQUIVALENT", if you can call it that would be either ceramic or Hurley (http://www.hurleyrotary.com/) apex seals, better water seals and coolant porting. Regular porting will mostly just add more power along with some other things like poor idle depending on how much material is removed. Max boost... well some guys run lots like in the 20s but those cars aren't normally driven every day. Work your way up to "as much HP as possible" and learn along the way. Ya really can't just jump right in and do that unless you pay a place to do all your thinking and choices for you. Some guys do it though. They hand over their car to a tuner, set a $$$ amount and say "as much HP as possible."

 

First off, do a lot of research before you start tampering with the car, because like a couple posts above, people are full of information... but not necessarily 100% correct information.

12 psi on the stock fuel system with the stock ECU equals one thing... fuel cut. It's not fun, don't do it. 14 psi on the stock fuel system, without ECU modification or an aftermarket computer equals one thing... time for a new engine. You will not get away with that. Most people don't get away with 14 psi anywhere but on the dyno, with race fuel, and ice on the motor. Forget about anything but stock boost until you've provided extra fuel.

That said, there have been people (since you asked about maximum boost pressure on the stock motor) who have run above 30 psi, and I know for a fact that the Ianetti 3mm ceramic apex seals have been run at 45+ psi. Boost doesn't kill the motor, inadequate fuel does. Detonate at 10 psi and you'll blow the motor, regardless of the fact that it's "only" stock boost. Even with ceramic apex seals, detonation will still take your motor out.

So first off, start with the reliability mods.

1) Check and find out if the car has had all TSBs (technical service bulletin) performed. If it hasn't get them done. Engine fires were more common than one might like from problems with the fuel lines, and there were recalls to repair these problems on the earlier cars, especially 1993 models. Your local Mazda dealership should be able to help you find out this information.

2) Get a boost gauge. In fact, before you buy the car, if you can rig up a temporary mechanical boost gauge (and thread the rubber hose out through a gap in the hood at the windshield) and find out what the stock boost levels are, you should do it. If you're not seeing (approximately) 10-8-10, the 8 indicating a drop in boost level as the second turbo is brought online at around 4,500 rpm, then you've got problems before you've even started. Get a boost gauge so you can diagnose boost problems.

3) Get a downpipe, ceramic coated if possible. Get the pre-cat out of the car, and if the main catalytic converter is suspect, replace it so that you don't have excessive backpressure and heat in the exhaust system. The pre-cat warms the enigne more quickly, but does little more than create heat. It can and will (if it has not already done so) bake all the vacuum lines controlling the sequential turbo system, making them brittle or prone to cracking. This is where a large number of boost response problems can come from. Get the heat out of the engine bay, because the pre-cat can (and again, does) bake your battery too, quickly killing most underhood batteries from the excessive heat. There have been several instances of batteries exploding.

4) Get an aftermarket radiator. These cars tend to overheat with extended heavy driving, and the stock cooling system is inadequate, especially for hotter climates. Get a Fluidyne (or other) replacement radiator and improve your chances of keeping the engine alive. Overheating is probably the second most common cause of engine replacement, shortly following detonation.

5) Closely monitor your water temp, but not with the stock gauge. The stock water temp gauge is weighted towards the center of its range. Therefore, by the time it starts moving to the high end, it's probably already too late. Get a "real" water temperature gauge and keep a close eye on your coolant temperature. If the gauge starts to rise excessively, stop doing what you're doing, and coast the car to let it cool down.

6) Get the stock intercooler out of the car. It's next to worthless, and acts more like a heatsink, sitting directly above the radiator, than an intercooler. Intake temperatures with the stock intercooler at stock boost levels can be very, very high if the car has sat (in traffic, for example) at idle for long periods. At speed, it's not as much of a problem, but it's still inadequate at best. Once you see how tiny the core of the stock IC is, you'll wonder what Mazda was thinking. If you intend to run higher boost levels, you MUST get rid of the stock intercooler. You can either choose between an underhood model (M2 Performance "medium" and "large" ICs, for example), or a front mount model. Keep in mind that a front mount model will not only collect rock damage much quicker, but will block air flow to the radiator also. FMICs are fine for drag racing, but are not the best solution for a street driven car or one that will see track use at extended high boost levels. It may cool the incoming air, but so do the underhood models, and they don't inhibit airflow through the radiator.

7) Once you raise boost, CONTROL it. Buy a *quality* boost controller and limit your boost. As mentioned above, without modification of the stock ECU, you'll hit fuel cut at 12 psi. With a downpipe and an upgraded intercooler, it's almost a given that you'll peak at 12 psi or a bit higher, so you need to control boost to safe levels, and above all, prevent boost spiking or creep. There are several models that people swear by, including the HKS EVC IV, EVC EZ, the Blitz controller, and the A'pexi AVC-R. Get a boost controller and keep your boost at safe levels.

8) While it isn't 100% accurate (since nothing but a multi-wire heated wide-band 02 sensor is truly accurate, but at high cost), you can monitor your oxygen sensor voltage to give you an indication of how rich (or lean) your engine is running. Anything below 0.86 volts is getting very lean, and if your readings are in the 0.82-0.84 volt range, you need to back your boost level off until you get adequate fuel. Anything from 0.80 and lower is almost guarantee to lead to engine replacement. 0.90 and higher is fairly rich. There are many manufacturers of Air/Fuel ratio gauges to monitor this reading, or you can (with a little work) hook up a multimeter to the wire lead at the ECU, which works for temporary measurement.

9) In combination with monitoring Air/Fuel ratio, you should also get a quality EGT (exhaust gas temperature) gauge and monitor that as well. Depending on your mods, people can give you a good idea of the ranges you should be seeing as far as exhaust temperatures and what's relatively safe. As with the coolant temperature, when EGTs start to rise dramatically, it's time to back off and let the car cool down. Which leads us to...

10) More fuel. Probably the most important and most neglected aspect of keeping your rotary healthy. If you're going to run higher than stock boost, you *will* need fuel modifications. The cheapest, a rising rate fuel pressure regulator (often called the "poor man's fuel computer) will raise fuel rail line pressure depending on boost level, and at higher pressures, more fuel is injected at a specific injector duty cycle than at lower pressures.

Speaking of injector duty cycle, the AVC-R boost controller from A'pexi will allow you to monitor the duty cycle of your injectors. Ideally, they should not be running at higher than 85-89% duty cycle. Doing so runs the risk of having them sticking open (creating a very rich situation) or stick closed (creating a very dangerous lean condition). If you're buying a used car, it is not a bad idea to have the stock injectors removed, cleaned and flow matched, or replaced if necessary. Your engine's health can literally depend on the condition of the injectors. If you're seeing duty cycles higher than these levels, it's time for larger injectors.

Which brings us to fuel system mods. The stock lines and pump are adequate for about 12-13 psi, but it is best to be on the safe side. Yes, there are people who run their cars at the track or on the dyno at 14+ psi (with the stock turbos) on the stock fuel lines and injectors, but always with a modified ECU (reprogrammed fuel maps for high boost) or a piggyback fuel computer, and almost always with an upgraded fuel pump and pressure regulator. And almost always with race gas, to increase octane and reduce the chances of detonation. On the street, the chances are very good that your car will not survive extended boost levels around 14-15 psi on the stock fuel system. Some get away with it, many don't.

Upgrade the fuel pump at the very least, and the lines, if possible. Many use the Cosmo (20B rotary) fuel pump, or the MKIV (fourth generation) Supra fuel pumps, which are almost identical. A lot use the Walbro fuel pump which outflows the previous too significantly, and many use the big Bosch pump (there are three models, the one you want has a screened inlet across the entire bottom of the pump, not the ones with a nut fitting for in-line use) to provide adequate fuel. The stock fuel lines are only the equivalent of roughly -4 aftermarket lines, so even upgrading at least your delivery line (there are three... one for fuel delivery, one for fuel return to the fuel tank, and one for the charcoal cannister vapor reclamation system) to a -6 (pronounced "dash 6") line is an improvement. Upgrading the fuel fittings on the tank outlet to aftermarket AN (Army/Navy spec) fittings and -8 fuel line is even better. The more fuel you can deliver, the better. Your return line can be smaller than your delivery line, but it doesn't hurt to upgrade that too, if you're really flowing a lot of fuel.

Upgrade the fuel computer. Probably the cheapest and easiest way is to have the stock computer modified. A piggyback chip is soldered onto the stock ECU motherboard and an EEPROM is "burned" with the fuel maps for your modifications. Many vendors can do this, but among them are Pettit Racing, M2 Performance, and XS Engineering. This is a good "intermediate" solution, but not ideal. The stock computer doesn't handle fuel delivery as effectively as it might, and a piggyback computer (PFS "purple" PFC, for example) or complete aftermarket computer (Motec, Electromotive, Haltech, Wolf3D, etc.) are better solutions, especially if you're going to upgrade to a single turbo, which will require even higher fuel delivery rates. The Power FC computer is also highly recommended.

Upgrade injectors. If you change the size of the stock injectors (as opposed to adding additional injectors on the intake manifold itself or on the intake elbow, as some kits do) and still have the stock computer, will you need to maintain the ratio in size of the injectors. The primary injectors are 550cc injectors and the secondaries are 850cc. Some people have had luck with upgrading the secondaries only, but some have upgraded both to 720cc primaries and 1220 secondaries (roughly maintaining the 1.5-1.6 ratio) and using the Peter Farrell PFC to control fuel delivery. But if you go with an aftermarket system, then it is much easier to control larger injectors and avoid the problems with tuning that changing the ratio between primary and secondary can cause.

11) Make more power? Replace your clutch. Or at least make sure that you have a rev limiter in place should the clutch let go. Get an ACT or Centerforce Dual-Friction clutch (or other aftermarket clutch) and don't even bother with the Mazdacomp 17% stiffer pressure plate or experimenting with friction plates. Buy an entire system and do it right once, the first time. The ACT clutch is highly recommended by many owners. The main problem with the stock clutch is that it's adequate for stock power levels, but can quickly be overcome (even in new, unabused condition) by additional power. Although the rotary engine loves to rev, there is a limit, and without a rev limiter (which can be removed when the ECU is reprogrammed), you need to make sure that you keep the engine from over-revving. Doing so can throw a corner seal or cause other internal damage to the motor, and the apex seals (under boost) tend to float (or pull away from the surface of the rotor housing) at revolutions higher than 8,000 per minute. When this happens, they cannot disperse heat, they can warp, and they can break, causing internal engine damage and damage to the turbo(s) as any broken pieces exit through the exhaust ports.

By adding a Crane HI-6 ignition computer, you can get a hotter spark to the engine, improve fuel economy (in some cases), eliminate the high end missing that some cars experience, and have a fail-safe for high rpm by setting its integrated rev limiter. There are several how-tos on the web for this mod and others.

12) Run spark plugs with a colder heat range. If you're going to run high boost, run NGK BUR9EQP plugs in both the leading and trailing positoins, and it may be necessary to go one heat range lower and run BUR11EQPs. A hotter plug retains more heat, which is exactly what you *don't* want under high boost, because it can lead to pre-ignition of the air/fuel charge before the optimal firing sequence. This cause an uneven burn (detonation), extremely high internal pressures, and will probably break your apex seals, especially with repetition. If you hear sounds under the hood like your engine is trying to make "popcorn", you need to back off immediately, but it'll probably be too late at that point.

Cheap insurance would be to buy the Jacobs knock sensor (more sensitive than the stock knock sensors) which will back out timing at the onset of the detection of detonation or "engine knock". It's not foolproof, but the purchase price is far cheaper than replacing an engine.

So to wrap this up, monitor your systems closely, provide enough fuel for the amount of boost pressure you plan to run, and with proper tuning, you can go a long way towards preventing the unwanted task of replacing your engine. These mods aren't 100% guaranteed to get 100k miles out of an engine, but they go a long way towards improving reliability and longevity. As always, increasing the power output of an engine does reduce its lifespan, and even with the best tuned system in the world, things can (and do) go wrong. There is one person I know who lost an engine at stock boost even with ceramic apex seals and a Motec system tuned by Mandeville Racing. Bad things do happen ocassionally, sometimes without reason.

Just keep an eye on your gauges and spend at least as much on your fuel system as you do on other mods, and you'll go a long way towards preventing anything like that from happening to you. And obviously, the more you err on the side of caution, the better off you'll be. I don't recommend more than 12-12.5 psi on the street to anyone running stock turbos, especially with a stock intercooler. It's just not worth it to push an extra pound or so of boost in order to make a little more power at the risk of losing an engine. Play it safe and you'll have a far better ownership experience.

Again, read all you can on the subject and educate yourself. Invest in an RX-7 service manual so that even if you don't have to work on the car, or don't want to do the work yourself, you'll still be educated on how the systems function and interact with eachother. If you ever do have to work on your own car, it'll pay for itself with the first use.

Search the Internet for information. A good place to start is Steve Cirian's web site.

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

Steve has captured information from posts to the "main" RX-7 mailing list (rx7@world.std.com) which is predominantly 3rd gen. oriented. There are links to how-to articles on other sites and on his site, pictures, information, many different opinions on everything from single turbo systems to suspension components.

Good luck!

 

That was a great post Jim! I even learned some useful things. Thanks for taking your time to type that, very much appreciated, even though I wasn't involved in this thread .

-Brian

 

Now if someone would just record it somewhere useful, I wouldn't have to type it over again next time...

 

That was one hell of an explanation:p

 

Hey Jim, damn, how much time did you spend on the explanation?

 

use the rate feature on the bottom of the page

 

Damn Jim!!!

That post should be required reading for all FD owners, especially newbies.....

My thanks for such an in-depth reply.

 

I recorded it somewhere useful...on my hard drive

Is it hard for some of you "Purists" out there to belive this is the same guy y'all berate for doing probably the most well-thought out V-8 conversion for ANY RX-7 ever done. Well it's not hard for me to believe. I know Jim knows his stuff when it comes to rotaries.

What is more unbelievable is that Jim keeps coming back to this forum to help them out.

Thanks Jim, you're a better man than I.

 

jim,

hell of a responce i must say, thank you for taking the time to enlighten me so vastly in the ways of the rotary. becuase of my lack of experience with this type of engine, your post was just what i needed. i'm actually saving it and will use it as reference and recommendation when i start to mod my future baby. i think your post here may actually save me some $$$ down the road. thanks again for the great info.

 

So, jim, got any inspiration to start a group buy?

 

Damn Jim you could make some money with more of wherever that came from.

 

Bumped for newbies.

 

holy cow...This thread is old. I wonder how long it took Jim to type that entire response?

 

If Jim was writing that for every newbie, no wonder he's so cranky now

Seriously, newbies, what he wrote is gospel. Just remember to not do any of the above until the stock configuration is maintained and running perfectly, with reliability fixes in place. Then you may proceed to Chapter 1, Verse 1, Book of Jimlab.

 

Thanks for unearthing this fossil...

 

This thread should be linked from the "Newbies/others please search / useful links" sticky.

-s-

 

Instead of linking it, I think Jimlabs specific post should be added to the very thread. A google search would yield the same results as found in the "Newbies/Others Please use search / Useful Links" thread, while this is far more in depth.

 

I think that I just learned more in an hour then I will learn ever in a life time. THANK GOD FOR Jimlab

 

You gotta hand it to Jim, he lays it out for you. So, lets give him a round of applause.

 

Excellent post, Jim.

I'd like to add that I've done everything Jim has suggested (and a wee bit more ) to good effect, but beware as this can be a costly process when done correctly and a _extremely_ costly process when done incorrectly. I've managed to sink about $40K in my car- not including purchase price. An appreciable proportion of this money is the result of trial-and -error.

Do what Jim says and it will save you a lot of headaches, dollars and motors.

Remark- I recommend against using the AVC-R for a moderate to highly modified sequential turbo car that sees frequent track duty. The controller has a difficult time controlling boost when the turbos are running in non-sequential mode (above 4500 RPM), particularly with high boost and no cats.

Good luck,

Gene