The boys over at Rotary Performance (rx7.com) are tickling the tender bits of my baby and installing a 3mm street port rebuild with a GT35R single in my '94 as well as a laundry list of other fuel related goodies. When I inquired to how much power I could expect from my build (mods to follow shortly), I was told ~350 whp. This number was slightly disappointing to me as my old stock motor/twins set up was thought to have run in the area of 300. Admittedly, 300 is a guess off the top of his head given the mods I had and his experience with rx7s. Chris informed me that 350 whp is about all you can safely get out of 93 octane, and going higher would require race fuel mix. I really thought the new engine, single turbo, and fuel goodies would net me ~100 hp and be in the area of 400 whp.

In my research, I have found a lot of variation in this in regards to 93 octane, boost, reliability, and whp. Sadly, there is often missing information on threads over a few years old regarding somewhat similar topics (dual pumps, injector size/duty, engine threw an apex seal and killed the dyno tech, etc.) I requested a "reliable, exciting daily driver", which it has been for 11 years, so that may factor into the numbers quoted. I know nearly nothing about tuning or power created from single turbos other than what I have learned in the last few days of searching and my car has never seen a dyno before. I would like to avoid water injection if possible. I plan to run 15 psi.

Performance Mods consist of:
3mm Street port
550/1600 injectors
Garrett GT35R Ball Bearing (T4, 1.06 Divided Exhaust)
RP Competition Fuel Pump
Koyo Radiator
M2 Med. SMIC
PowerFC + Commander
GReddy Profec B
3" down pipe + Mid-pipe
Greddy Evo Cat back
All emissions removed

Is 400 rwhp on 93 octane unobtainable safely with this build? Is the pump gas truly the limiting factor? Is 350 considered quality numbers for a build of this type or is that a very conservative tune to produce a reliable daily driver? I have heard nothing but great things about Rotary Performance and Chris seems exceedingly knowledgeable, so I do trust his judgement (I am finally trusting someone else with my car after all) but I'm curious what you guys think and what your experience can tell me.

 

No. It can definitely be attainable.
Pump, and more importantly, the tune.
Reliable Daily Driver. Nothing wrong with that at all.
You're close to San Antonio, and several e85 Stations. Get bigger injectors,
and Run e85. You'll easily have 400whp with the higher boost attainable from
the high octane and cooling properties of Ethanol.

YMMV.

 

^ +1 everything.

 

first off, congratulations on working w a first class outfit. Ari and co have been doing it for as long as the FD as been in existence. they are still in biz because they are honest and competent.

"I know nearly nothing about tuning or power created from single turbos other than what I have learned in the last few days"

compare your honest statement w the experience of the staff at RP. this is not meant in any way to be a negative towards you. actually you should be commended for being honest.

now that we have that out of the way... let's address your actual question:

lots of setups just like yours (and you have made many good choices as to hardware) are making 400-500 hp. your turbo and overall setup will get you there. so why is RP talking 350?

simple:

"I would like to avoid water injection if possible."

you are asking the right question in the title to your thread... "limits of pump"

it is all about combustion chamber pressure/heat (CCP)

there is a common misconception re the turbo'd rotary.

it came from Mazda at 255 flywheel hp. that is 217 rwhp.

350 is a 61% increase. 400 is 84%.

because it is so easy to add airflow in a turbo'd situation, and airflow is hp most anything is attainable... (often for a short period of time)

my friend Jose Le Duc is making 1100 rwhp from his 2 rotor.

airflow/hp is easy.... making it live, that is an entirely different proposition and it is here that fuel CCP becomes the dominating factor.

the rotary functions like a 2 cycle motor in that everytime TDC arrives in front of the sparkplug we have a power/heat/pressure event. (4 cycle) piston engines, unlike our rotaries have a cooling (non power) event every other TDC.

rotaries generate about 1650 F EGTs... piston engines about 1320.

given the above additional heat considerations, and the fact that all gasoline (race as well as pump) autoignites at a mere 450F... you need to add cooling into the combustion chamber.

do that and it all changes. water has immense cooling properties...

water 8087 BTUs cooling per gallon
gasoline 900
methanol 3340

you don't need much, 300-500 CC/Min will work well for your app.

in addition, the rotary gets clogged up w carbon. water cleans all the carbon so it is a win win.

since water is not a fuel and is a negative offset to fuel BTUs of energy, water will cost a few hp. you just run another pound or two of boost and end up positive net.

w a proper water setup you can easily and reliably make 400 rwhp.

without some form of AI at 400 i suggest you keep your engine builder's number in your speed dial.

more on the subject:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/making-case-rotary-powered-fd-fix-806104/

you might also spend some time in the forum's AI section.

good luck, you have a lot of the right stuff on your FD. ATM, it is missing just one key item...
add it and enjoy a reliable 400+hp.

howard

 

Go to a generous dyno and you'll get 400 rwhp for a car that gets 350 rwhp elsewhere. Don't stress about the number so much. Just go by how it actually feels when your on it. The new setup is going to be A LOT faster then your old setup with stock twins and stock motor.

thewird

 

as ^ is saying, the number is the number--to an extent anyway. Dynos can vary a lot even if there's nothing "wrong" with your setup. It's pretty simple. If RP tells you 350 and you get 380 or 400, then they have exceeded expectations and goals. If they tell you 400 and end up with 380, you are going to be disappointed.

As Howard is pointing out, these engines weren't designed to make that kind of power. A high combustion chamber pressure increases the likelihood of a knock event, especially in the trailing portion of the combustion chamber which is highly prone to knock. These engines don't have a "smart" modern engine computer that can protect the engine if something goes wrong. So something else has to be done.

Besides having a good cooling system, you can increase the fuel quality, you can inject something like water or methanol, or you can run a conservative tune on pump fuel. Those are your three main choices if you don't want your engine to fly to pieces in a short period of time. Each choice has its drawbacks. Increasing fuel quality has cost and availability concerns. Injecting something increases complexity and hassle to an extent. Running a conservative tune hurts output to an extent.

 

I made 360 @ 13 psi and 420 @ 17 psi on the exact same set up you have. On 93 octane. Only difference being a microtech ecu. Even have the RP fuel pump you have. My old set up was 16 psi on stock twins @ 375 whp. The car felt better on 13 psi than the 16 psi stock twins. At 17 psi it was really fun! It ran great for 5000 miles like this. The motor popped @ 13psi and I could tell the fuel pre ignited Victim of bad gas. That motor had 20,000 miles of *** pounding abuse. I am now going to run 325 cc's of 50/50 water/meth as a safety margin. Believe everything we are telling you. A simple A I system is a really good idea. Even for 15psi like you want. G

 

I can tell you that RP is an A+ outfit and they like to tune for safety, reliability and whp. I know they don't like to push the engines too much. I would think they wouldn't want the liability of **** breaking on their dyno tune session. A side note 350whp single turbo WILL be ******* fast. Mine got tuned to 330whp. I was disappointed when chris told me that until I drove it......If it's the number you seek and not reliability then there are some really good tuners in Houston/n Texas areas

 

Wonderful information. Thank you all kindly.

I'm definitely not a "LOOK AT MY DYNO SHEET!" type of individual, so it's not much of an issue, I was just a little surprised, things didn't initially line up in my head. I am very much looking forward to feeling how this new set up puts the power to the ground. The guys at RP have had nothing but the best reviews from some of the most senior and trusted members of this community imo, and I've known of them since I got my car over 11 years ago. This community is the only reason I finally let someone else dig into my car, since you guys trust them.

My original reason for neglecting the AI was the thought it's just one more thing to go wrong/clog. I like the K.I.S.S theory and I feared the forgetful nature of my driving style would cause it to be more of a hindrance than help. Late for work, hop in the car, oh crap I'm out of water, boom. I see now this is only the case when pushing an engine to the breaking point and AI is being used to keep it together, not simply as a safety blanket. Also, it seemed to be counter-intuitive to spray water into a car that gets mighty pissy about low quality pump gas. Anyway, after the crash course I see the errors of my ways, I'm sold. Specially after the 106+ degree summer we just had.

New problem, however. Time is of the essence. Working 2 jobs, and fighting to get into medical school consumes 99.8% of my time currently, which leaves little time for DIY/proper research and is forcing me to be a lot more impulsive than I'd like. Regardless, I need to pull the trigger now and get the equipment to RP so they can install while the car is there. These kits are very confusing with my current knowledge base (but I'm learning as quick as I can) and most seem incomplete or leave me questioning compatibility/tank fitment/what else I need that I don't know of/etc. I didn't get time to talk to Chris about it today (He was busy, I will discuss it further with him tomorrow) but I spoke with Mary who said that RP did not have an AI kit.

As such, I turned to Jason's site and found this AEM kit. (http://www.rx7store.net/product_p/aem%2030-3002.htm) Kit says it includes everything I need and has the boost-dependent, variable-flow progressive controller to determine the amount of water/methanol mixture. Is this an acceptable kit or can you recommend a better setup that I don't have to surf around for days to piece together?

I greatly appreciate all of your input and help. Thanks guys.

 

i run my 35r at 19psi on 93 and no AI(100%humidity here), this engine made it 17,000 so far...

Y are you using the crappy 1680cc injectors??? they are a peak hold injector, not saturate type, pfc is not designed to control peak hold injectors. They make a better option now, Why not id 2200???

 

Ehhhh? Not sure if serious. The marketing has gotten to you.

1600cc Bosch are a brilliant injector. They have excellent pulse width response AS A SECONDARY INJECTOR which is what they are used as... I have found no problems whatsoever operating them between 30% and 90% duty cycle even when operating in a twice per RPM injection strategy.

The impedance is in the 'grey area' between peak hold and saturated. You can operate them as a saturated injector with no inline resistor if you computer is anywhere near decent. They are staged out until 3000+ rpm is on board anyway....

Before anyone enters an argument with me about electrical/electronics engineering, I write digital signal processing for a paid living, between testing and calibrating instruments worth more than just about any car on this forum.

 

If you cant get over 400RWHP on 93 octane then you have other issues. If worried about just using pump gas then get a Meth kit which is cheap.

 

generally speaking, the main issues with the older pintle-type injector even as a secondary injector are atomization and a higher tendency to clog up. In this application it doesn't matter as much though. The atomization issue--well it's hard to measure that in the real world (not a bench test) without the proper equipment, and as you've alluded to, injection timing plays a role. The PFC has no options to control injection timing so that point is essentially moot.

The EV14 uses a ball valve and an orifice plate design that has less tendency to clog. They do cost more though.

 

The AEM kit is a nice simple system and running pure water just as a safety blanket, as well as an engine steam cleaner is a good idea.

thewird

 

1600cc Bosch EV-14 injectors

http://www.youtube.com/watch?v=URuooVn2lw0

What does an ID2000 spray like?

 

I think you mean EV1



I think the EV14's have their place in performance applications. I'm using ID1000's for primaries, and they idle quite nicely. But as mentioned, for a secondary injector, there is absolutely nothing wrong with the older EV1 1600's.

 

There's a heck of a lot more to a fuel injector's performance/behavior in the real world than what is normally talked about on the internet. Lots of literature exists on this stuff--for our sake, this is mostly an academic discussion. There are factors like the Sauder Mean Diameter of the spray droplets, the droplet distribution, the angle of the spray cone, the injector sac/injector slug, the droplet momentum, the distance of the injector from the intake port, the aim of the injector spray along several axes, intake port air dynamics, wall film effects, and injection timing. There's also the effect of the diffuser plates and air bleeds, systems that Mazda already installed. Zhao, "The Spray Characteristics of Automotive Port Fuel Injection--A Critical Review," 1995 covers all these topics. The Bosch Automotive Guidebook 8th edition (2011) has some good discussion of an EV14 injector in the chapter on mixture formation.

I don't know the Bosch part # that ID rebadges/modifies as the ID2000. I'm sure they are a single spray, conical-type pattern like the EV1 injector you posted above. I don't know what the angle of the spray cone is, or the Sauter Mean Diameter of the droplets, or any of that other stuff. I do know that the EV14 injector is inherently less prone to clogging however, and the ball valve/orifice plate design produces smaller Sauter Mean Diameter droplets than a pintle-valve injector. The EV14 ID2000 is a universal part. The EV1 is a universal part. Neither are anywhere near optimized for individual applications, but the EV14 is still a newer design (but more expensive).

Again this is all academic... I have Bosch 1600/1680 in my own car, the exact same ones shown in the Youtube video above.

 

Jobro -Not saying the 1600s can't be used properly, crappy is not the right word. It just seems the newer injectors are a better option given they flow more and don't need the resistor. More fuel and easy.

I have noticed reading these fourms that the PFC and 1600/resistored injectors seem to have a high rate of failure buring out injector drivers. Anyone else notice this? Any inbalance in the impedence is going to strain sumting.

Just stating what I notice. Not the marketing that sells me. Its the 600cc of extra fuel.

 

Probably due to installation errors or other mistakes more than anything else. There's nothing inherently wrong with a saturated driver and a resistor for a low impedence injector--you just don't have the benefits of a peak-and-hold driver. A lot of cars came that way from the factory, including the 84-87 1/2 Rx-7 models. I have been using the Mazda OEM 6 ohm resistor pack on my 1680cc injectors for a few years and have not had any problems. I am using a Power FC.

Also, peak-and-hold style drivers are being used today on Gasoline Direct Injection engines utilizing solenoid-based injectors (as opposed to Piezoelectric). The driver uses 60V to open the injector and then the voltage tapers down. The Ford Ecoboost engines are one example of this.

 

I was a little mixed up on the injector types and how they work. Thanks for clearing that up.

 

Interesting developments on the injectors derail, that is some rather cool information. I’ll be honest; I did not do any research on the injectors beforehand. I trusted Chris to know what injectors were the best options for my application. I told him to put what injectors he thought I needed and I went with his recommendation. I figured he knew best.

In regard to AI:

My confidence has been shaken a bit. When I called and spoke with Chris, he did not seem thrilled by the idea at all. I got a vibe of “why?” from the conversation. He did state that he didn’t like gimmicks and thought the practice of using water/meth injection in lieu of race gas was unwise (paraphrased, of course). When I told him I’d have him tune the car without AI running, then use it as an added safety blanket, he didn’t outright shoot the idea down, but I still got the feeling he was telling me it wasn’t really necessary/worth it. He stood firm to his 350 hp is the most he would want to tune the car for while using pump gas, after that you need to get fuel from a can. While I would love to have high/normal/low boost settings ready at the flip of a switch, it doesn’t appear like he would feel comfortable tuning the car higher than 350 with AI support anyway.

Eh, well I’m still on the fence about it. It does seem like such a good idea… I really wish I had more time to sit around and research this.

Anyway, I guess the overall answer is that the build is fully capable of 400+ whp, however, this number (and yes I agree it is just a number, but I’m using it as a point of reference) is unreliable/unsafe for the engine without utilizing race gas due to fear of pre-detonation even with 3mm apex seals. AI, when utilized to negate the necessity of race gas, is considered an unwise gimmick of questionable reliability by one of the better/well established rotary experts and is not recommended.

That said, something tells me that I’ll feel the itch to kindly disregard that wise advice and a craving for the extra power of higher boost will surface at some point…which makes me think I should have the AI installed and ready for my juvenile side to rear its ugly head and muddle with my sense of reason.

 

i dont find that hard to believe at all, my tuner is very good friends with the group over at RP and he also shakes his head at A.I. although he tuned my car to 396 at 15lbs and it worked great. I have recently upgraded the fuel system to the 550/1600 bigger lines and quality fpr and want to add A.I. to get some power in the 450 area. I am not sure how he is going to handle it.

 

I have heard mostly all good stuff about AI. I think in your case he seems its just not necessary if you have a good tune...

 

Of course you can run a decent amount of boost on pump gas and make great numbers, many people have and there's nothing wrong with it. But from a tuners standpoint I'd urge any person to get water injection just for the safety/reliability it adds to the every day John Doe driver, that knows just enough to put the higher octane fuel in his car.

 

Shakes his head? In what way? AI has been proven over end over again. Im mad I didnt do it 10 years ago.