I'm planning an N/A build with 2x ID1000 injectors only.

How much WHP would just those injectors be able to provide?

 

At what fuel pressure? Consider that the stock 4x550 on the T2 is good for at least low 200s to the wheels on a turbo engine at only 36psi (2.5bar) stock pressure.

I'd say you could get close to 300 to the wheels running the typical 43.5psi (3 bar) that the ID injectors were designed for.

 

Wonderful. I'm shooting for 250whp on a streetport, so 300 is a good error margin. Thank you very much!

 

it depends on the VE of the engine, redline RPMs, fuel pressure, and the mixture you want.

the mixture you want part needs some fudge room, for example if you decide your target AFR is 12.5, you want to be able to have enough duty cycle to go richer, say 12 or 11.5. this is probably more important on a turbo car, but still. i'm not mentioning BSFC here, its related to the mixture and the port/airflow of the motor, so its complex.

redline was can assume is around 8500, as a worst case. lets say 12:1 afr, on a side port this should put you around .72 BSFC*. lets say @80% duty cycle, this gives you a little head room, like if we're wrong, you can go to 85%

depending on rpm HP peaks at, you could do 225-230 at STOCK FUEL PRESSURE.

http://www.not2fast.com/turbo/glossary/turbo_calc.shtml

*ive looked at a bunch of dyno sheets and things to come up with the BSFC number, side ports kind of stink, even @13:1 the BSFC will be in the .68 area. a peripheral port will be about .5 around the power peak, which is much better. turbo rotary is .8 or worse

so i think 2x1000 injectors is perfect

 

I'm used to turbo piston motors with a BSFC of .55. I had no idea a p-port would get to .5, that's really very impressive.

The engine is going into a Miata, so the stock fuel pressure is already 43.5, so that's no effort to get. BSFC of .68 is just... wow. Terrible. I didn't know rotaries were /that/ bad, to be honest. And .8 for turbo.

Been reading up on the AFR thread here as well, I don't think I'd need to get down to 11.5 or 12, I was thinking that with later rotors I'd likely be shooting for 13.2 to 14:1 at WOT.

In any case, I'll need an aftermarket FPR, so if it's not enough I can always do 70psi.

 

https://www.rx7club.com/rotary-car-performance-77/typical-bsfc-rotary-227445/

 

Thank you for the link.

Though I wish I could get a .45 BFSC. :P

Also, did you get an AzRR rebuild? I've been considering going with them, as they're local and everything I've read about them is quite good.

 

i've known tom and glen for a while, they are good people.

i've always built my own engines anyways, so i just had them balance it, most of it was new parts anyways.

 

BSFC should be in the range of .5-.55 for NA rotary.

.65 or higher for turbo

2 1000's should get the job done.

My motor seems to like AFR's between 13.5-13.8

 

.5-.55 seems really low for a rotary. That's not much different than a piston engine, and .65 for turbo contradicts what I've read elsewhere...

Also, GSLSE-YA, did you end up keeping your S5 rotors or switching to RX8? I did some research on your old threads and couldn't get a definite picture of what you're running now. I've been planning to run RX8 rotors, but looking back, all I can find is two year old information about RX8 rotors not being as good. Not sure if those problems are solved or not.

Also, love your car. Saw the pics a year ago and they helped push me towards this project.

 

I got the figures .5-.55 from the book "Street Rotary". It is probably not representative for a stock NA motor with stock attachments. But your setup will be far from stock with close to 250whp from a streetport.

I still have the RB lightened S5 rotors but with an rx8 e-shaft & 2mm ceramic apex seals.

Using rx8 rotors with older housings and irons cause sealing problems because the way the rotor is shaped for the side exhaust ports in the rx8. (correct me if i'm wrong)

Thanks for the complements on the car. I just started working on it again. It's been sitting since Nationals last year. Getting it ready for the April Buttonwillow event.

 

Keep us posted on your project.

I should have some updates for mine next month.

 

Not trying to shoot your hopes down, but I thought I should mention that it's going to be difficult and maybe impossible to get 250whp with a NA 13B streetport.

Have you considered going bridgeport? Bridgeport's (non-J or D bridge)are fairly cost effective and still have good torque (not too peaky). Typical results are between 230-270whp, depending on size of ports, exhaust, etc...

 

ID used to have a horsepower calculator up on their site, I'll see if they can put it back up.

We're a dealer and I've got it on my computer here, it takes into account BSFC, specific gravity of fuels, fuel pressure, firing mode, dead times of the injectors. The results are in a table with horsepower vs. RPM, super easy and accurate!


EDIT:

The results-

Note - keep in mind these are in calculated flywheel hp, but Paul seems to think they quite closely match the liberal numbers of a Dynojet after many years of comparing with engine dyno's. Also, I think Paul built in a bit of cushion to the absolute duty cycle maximum of the injectors to account for people trying to push right to the edge.

9000 RPM redline

Super Conservative .7 BSFC
45psi - 197
60psi - 221.2
80psi - 245.8
100psi - 263.7

Less Conservative .6 BSFC
45psi - 229.9
60psi - 258
80psi - 286.7
100psi - 307.7

 

the BSFC of an n/a is certainly going to be less than a turbo engine of a similar power level

 

Difficult, certainly, but I have everything figured out except the exhaust and possibly spark. I've not researched if I need to upgrade coils, I know it's a common mod in the RX8.

If I get NA S5 rotors or RX8 rotors, that should give me enough compression.
With the ITB's and RB intake manifold, that should give me enough intake.
If I go with a cosmo housing that should let me port out enough.

I've considered going a bridgeport, but I want the engine to last as long as possible. 100k street miles and a track day every month or so is a goal. I like when things just work and I don't need to mess with them as much.

 

I've actually always used this calculator:

http://www.rceng.com/technical.aspx

Found that it's quite easy and accurate. At .55 BFSC it says I'd need a PSI of 50 to keep an 80% duty cycle at 290 flywheel horsepower.

 

Yeah don't use that RC one, it's too generalized, not to mention RC.. well I'll hold my comments lol.

Use this one.

http://www.injectordynamics.com/hors...alculator.html

Also you would be better off running 2x 725's at a higher pressure (with a pump that can support)

 

I didn't want to be the one to say it

But hey, one person got 230 wheel with a street port, so there's probably 20 more whp left in it because, I don't know, lake effect or something.

I will say this much: My half-bridge did not make any more power than the street port it started out as (both ~170-175 whp on a Dynojet - with 2x680cc) but but BUT the half bridge was way more drivable than the street port was. The street port made peak torque at about 6000rpm. So did the half bridge, but the HB was making more torque at 3000 than the street port did at 6000. The torque peak was basically the highest elevation in Kansas Those two little eyebrows were worth 20-30 "wheel" ft-lb. More torque for the same horsepower means lower RPM means higher engine longevity, all else kept equal.

The half bridge probably could have made a lot more power if the exhaust wasn't so crappy, but fat torque rules over horsepower numbers, at least until you have $20k to spend on a transmission. Plus, engine longevity becomes a factor... if you want the engine to stay together for 100k at the kind of RPM levels regularly seen, you're going to want ceramics. I haven't run Mazda 2mm seals for that long, but the Atkins 2mm seals appear to be done by about 50k, and they are pretty harsh on housings too. (They can definitely withstand sustained high RPM though, but spring seat wear is rapid) I have strong doubts as to if carbon 2mm seals will last even 50k. At any rate, you'll have the side seals and oil rings to worry about too.

Everything I've seen has suggested that the RX-8 rotors are a high RPM power liability, not a power benefit. Oddly enough, I've also seen S4 T2 rotored engines make silly power N/A. Makes you wonder if compression is all that it's cracked up to be, when it comes to rotaries and high RPM.

 

Peejay home come your GSL-SE weighs 2750lb loaded. My full interior GSL was only weighing 2552lb with full load of petrol, spare tyre, full interior, 48lb of battery. And myself back when I weighed 220lb's. Why is the 200lb / 90kg difference.

Is that what a gen1 rollcage weighs?

 

No rollcage. (And it's not a GSL-SE) The 13B added weight, the front mount oil cooler added weight, the skid plate added a ****-ton of weight (probably 50-60lb - it is roughly 60cm by 60cm by 10mm and steel) and there's also 200lb of driver in there too. I also never run it in any competition below half tank, usually with a full tank of fuel. There is also a LOT of steel added in to the rear suspension, while only a little has been removed. Slice out 22 gauge steel, add it in as 11 gauge

Plus US spec cars tend to be on the heavy side, ESPECIALLY the Series 3s. I understand that there were multiple layers of steel added to certain points in the bodyshell. The Series 3 interiors are markedly heavier feeling than Series 1/2, with additional sound deadener everywhere. It's like the difference between 240Z and 280ZX. I do miss the days of driving my Series 1 that weighed a verified 2400lb with me in it. 'Course, that was ten years ago (!!) and I weighed only 190 back then I think the headliner in that car was a sheet of vinyl glued to the inside of the roof, not some heavy felt/cardboard/deadener monstrosity.

Do you guys have the huge support beams in the doors? I know this is one reason why US spec cars from the era always weighed more than, say, European or Japanese models.

 

No, not lake effect.

He did 230whp on a modified stock IM, where I'd be using an RB IM with ITB's.

He's also on low compression turbo rotors, if I remember correctly. FC vs RX8 eshaft should be nothing. No hardened stat gears means he stops at 8900rpm as well.

There's the potential for more, though if I don't make my goals I'll still be happy... but aim high.

 

^^Is that a local motor you're talking about? Sounds surprisingly similar to a friend of mine's in a little red RS car...

I saw you mentioned AZRR for the build. Glen is a good friend. He is always crazy busy, but builds amazing rotaries, would definitely recommend him.

 

No, I'm talking about this guy:

https://www.rx7club.com/naturally-aspirated-performance-forum-220/make-230rwhp-streetport-13bre-n-818133/

I'm sorry, what do you mean by RS car?

Also, I tried searching google for your place of business or a website or something, nothing came up?

Sent an email to AZRR about this build as I'll in the more immediate future need an exhaust made. No response, so I'm not sure. Heard good things about them, though.

 

Ahh, it's just an SCCA RS class 1st gen that a friend has in North Phx.

We're actually still working on getting our website setup.

Glen also runs a shop named Boost Flow that builds really nice manifolds and they do amazing fab work, so I'm sure he'll be able to help you out with an exhaust. I know he was sick when I talked to him a couple days ago, may just take a bit to get a response.