RICESP Water Injected RX7

[PobodY]

Is that because it's a rotary?

[RICE RACING]

Originally Posted by madbouncy

In the picture it looks like your manifold pressure is 30psi and the exhaust is almost 38 psi. That doesn't seem like it's getting that high compared to a lot of logs I see on other cars, mainly subarus. Exhaust pressure never really seems to get talked about a whole lot so I'm definitely interested if you have suggestions on what you look for. For my subaru the recommended ratio is around 1.5 to 2 and they don't consider it high until around 60psi. Obviously the RPM is turbo dependent so that I can understand getting too high and is easier to know when you're going too far.

Also, do you think a lot of the exhaust pressure has to do with overlap? Say an engine with almost no overlap could get away with more exhaust pressure than a car with moderate or extreme overlap? From a theory standpoint that would make sense to me but the theory only talks about a concept and doesn't give any insight on an actual optimal setup.

Lastly, is the boost engine that is at 30 psi the actual manifold pressure or is it before the intercooler and everything?

- Matt

The boost is measured in the inlet manifold, both the MAP sensor and the boost gauge read the same in that regard, its the true boost pressure the engine see's

The pressure in the exhaust manifold was always well below 1:1 at boost pressures up to 22psi then as I went above this level and to 26psi it started to show an upwards rise along with a non equal rise in power level, and at 33psi and above it a fair bit higher as shown (even in the 30psi boost log).

Rotary engines due to open ports 1/3rd longer combustion duration events and common shared cycles per rotor are far more sensitive to "typical" back pressure levels as you would read about on piston engines, they fall off the performance curve far far easier and quicker. So always a rotary engine needs a far bigger turbine wheel and rear housing to deliver the power you would think achievable on a similar turbo. It's just a negative of this engine type.

[Liborek]

Originally Posted by RICE RACING

Rotary engines due to open ports 1/3rd longer combustion duration events and common shared cycles per rotor are far more sensitive to "typical" back pressure levels as you would read about on piston engines, they fall off the performance curve far far easier and quicker. So always a rotary engine needs a far bigger turbine wheel and rear housing to deliver the power you would think achievable on a similar turbo. It's just a negative of this engine type.

Peter, do you believe that lowering of backpressure would allow you to run substantially more power from this compressor? Based on compressor speed, its already operating past its choke line, which happens to be about 75 lbs/min, so any gains would have to be result of direct increase in efficiency - decrease in BSFC from lowered internal EGR and pumping losses.

I'm also interested if porting style can directly impact efficiency, more specifically efficiency of turning air into power. For example R26B with its 700 HP@9000 rpms would have to have ridiculously high VE% to produce such power, considering widely accepted claim, that rotary engines produce about 7.7 HP from each pound per minute of airflow. Your own numbers you posted earlier (0.681 BSFC at 10.2 AFR) would indicate 8.6 HP from each pound per minute.

Any input would be appreciated

[RICE RACING]

Originally Posted by Liborek

Peter, do you believe that lowering of backpressure would allow you to run substantially more power from this compressor? Based on compressor speed, its already operating past its choke line, which happens to be about 75 lbs/min, so any gains would have to be result of direct increase in efficiency - decrease in BSFC from lowered internal EGR and pumping losses.

I'm also interested if porting style can directly impact efficiency, more specifically efficiency of turning air into power. For example R26B with its 700 HP@9000 rpms would have to have ridiculously high VE% to produce such power, considering widely accepted claim, that rotary engines produce about 7.7 HP from each pound per minute of airflow. Your own numbers you posted earlier (0.681 BSFC at 10.2 AFR) would indicate 8.6 HP from each pound per minute.

Any input would be appreciated

I think so yes it will have a net positive effect on power lowering the pressure acting against the rotors.

While I have never put numeric figures to the level of power to air flow as I'm not too sure exactly how much air flow goes in after I spray water into the front of the turbo, I guess it would be closer to high 7 or 8 than 8.6. But that is very arbitrary as the effects of power generation are always limited when running street fuel from the ever present threat of detonation.

The next steps would be a different turbocharger, and changed specifications for the engine porting (nothing too major in timing, just optimization and fine detail work). There is more in it to experiment with which I would like to do in future, but not using this turbocharger. The base line of engine performance and range is good, I would not deviate much from it really, as its not really necessary for a nice street car.

[madbouncy]

Originally Posted by RICE RACING

I think so yes it will have a net positive effect on power lowering the pressure acting against the rotors.

While I have never put numeric figures to the level of power to air flow as I'm not too sure exactly how much air flow goes in after I spray water into the front of the turbo, I guess it would be closer to high 7 or 8 than 8.6. But that is very arbitrary as the effects of power generation are always limited when running street fuel from the ever present threat of detonation.

The next steps would be a different turbocharger, and changed specifications for the engine porting (nothing too major in timing, just optimization and fine detail work). There is more in it to experiment with which I would like to do in future, but not using this turbocharger. The base line of engine performance and range is good, I would not deviate much from it really, as its not really necessary for a nice street car.

Do you plan on running this motor until it's shot or will you probably just go until you decide to change the porting? I'm sure a lot of people would love to see a high power rotary engine hit 100k miles and still be in good shape when torn apart.

I was looking back through your setup and I was curious what you use for balance when you're welding aluminum? I was welding some tubing and it seemed like no matter how much I cleaned and scrubbed it immediately pulled black soot when I started to weld. I was at the point where I was doing cleaning passes with 55% and then would go back and do the actual welds at 70%. I was able to do the welds at 60% without the cleaning pass and I used some recommended settings I found from a tig welding site but my penetration was garbage and my puddle was growing huge for the little bit of penetration it was getting.

[RICE RACING]

Originally Posted by madbouncy

Do you plan on running this motor until it's shot or will you probably just go until you decide to change the porting? I'm sure a lot of people would love to see a high power rotary engine hit 100k miles and still be in good shape when torn apart.

I was looking back through your setup and I was curious what you use for balance when you're welding aluminum? I was welding some tubing and it seemed like no matter how much I cleaned and scrubbed it immediately pulled black soot when I started to weld. I was at the point where I was doing cleaning passes with 55% and then would go back and do the actual welds at 70%. I was able to do the welds at 60% without the cleaning pass and I used some recommended settings I found from a tig welding site but my penetration was garbage and my puddle was growing huge for the little bit of penetration it was getting.

TO run the new turbo I have I'm going to run the exact same engine but I will optimize the porting of the engine enhance the characteristics I have proven here over the years, these are just minor detail things, no big wholesale specification changes, more the same philosophy of using the turbocharger to increase the pressure ratio and thus the oxygen getting into the engine. I'd never cover 100k miles in my lifetime in this car (it's too special and rare to do that with) but the amount of kilometers I do to prove the concept is many more than most others anyway so that will suffice me.

For the welding advice, I use a Kempi Machine, I need to look at what I have in the program settings for Al, I did a a few years back change it to pulse TIG where it worked far better for me.... if you want you can E-Mail me for more info.

[Liborek]

Originally Posted by RICE RACING

TO run the new turbo I have I'm going to run the exact same engine but I will optimize the porting of the engine enhance the characteristics I have proven here over the years, these are just minor detail things, no big wholesale specification changes, more the same philosophy of using the turbocharger to increase the pressure ratio and thus the oxygen getting into the engine.

I could guess some work in port runner itself and slightly earlier intake opening? Maybe later exhaust closing?

As for the turbo, I'm guessing BorgWarner EFR 9180

Calculating the power from certain airflow is pretty easy, I do believe that your power measure is most accurate apart from engine dyno so this is covered. Then its just matter of knowing exact fuel flow and exact AFR at given point. Problem is that methanol contributes to fuel energy value, so true BSFC is higher.

Too bad we don't know exact mass flow through the compressor. Cooling of the compressor inlet certainly does increase the mass flow, but I'm not so sure what happens when the whole charge gets saturated and any more injected fluid of same vapor pressure will remain liquid.

Time to read about wet compression lol

[RICE RACING]

Borg Warner no. But the new turbo is secret squirrel

"Detail work" to ports I wont really divulge, but stock attributes need to be maintained to have the wide and flat power range I have now (secret to the car being so fast) despite being a few hundred hp less than some others "claims" but again as you say its not that hard to work back/out etc.

I do like the way I measure the power too, its factual and correlates across all of the tests I have done and best bit is it directly relates to the measured performance (which is a great cross check). I've never had an odd or dubious result, which is as to be expected as its derived from the vehicle performance anyway............. so unless you cheat yourself with a parameter then its all going to reconcile at the end of the day.

[Grant M]

It is bugging me trying to work out how you will maintain the same power band of the standard port after actually changing some of the port shape.

Now you can change the exhaust port with out changing the timing by making it a bit wider. Now the only thing I can think of at present for increasing your intake without actually changing the ports themselves is to use scalloped rotors opening your ports earlier and closing a little later.

I will be looking forward to what you do with the porting, if you do decide to share it with every one

[madbouncy]

You should check out this thread on porting

http://www.nopistons.com/showthread.php?t=29264

It was started by Judge Ito but later on Rice Racing posts that he's been using the same port for a long time and has some pictures. It doesn't necessarly mean it's the port in the engine he is running now but he said he had been using that port for 11 years so he obviously is a very big fan of it and is probably doing updates to the port on the engine to experiment. Post 75 I believe has the pictures I mentioned.