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This is a quick preview of the mockup for my racing engine. The car is an E-Mod SCCA auto cross car.
I bored the PP holes with a drill press and used copper for the intake plumbing as well as the housing port. This thing is a very powerful beast. It is fueled with an old school Holley Projection unit (670 cfm). The turbo is from a 2.3 Ford like a 85 T-Bird.
The irons were also resurfaced on the drill press with the help of a homebuilt turntable.
A large series of photos are available on my facebook page which should be open to the public for viewing.
That is the smallest turbo I have ever seen on a rotary. Must spool very fast especially with p-ports. Should be good for 250rwhp or thereabouts.
If you ever want a mild upgrade you could put a stock FC HT18 turbo on. Not much more compressor, but much bigger exhaust side- should do 300rwhp on your set-up.
-edit- An amazing upgrade would be a used EFR 7163 from an IRL car (~$650). Good for solid 400rwhp and spool like what you have now.
I was considering a BW EFR6258 as a replacement some day.
The turbo does spool quickly and I figure mathematically that I should get at least 350hp at 8000. I wanted this to have a very wide power band 2500-8000 and it does. It is a bit of a trick to adapt a pure alpha-n system to accept boost, however.
The injectors are rated at 80# at 21psi. I have the base fuel pressure at about 35psi and boost referenced to the turbo outlet. I made an electro/mechanical device to advance the TPS reading during boost. I am installing a blow off valve to try and make this device 'LET GO' when the throttle is closed. It is kinda scary when you are trying to stop and it feels like a truck is pushing you......
Whereas an NA p-port rotary might also make a peak 250rwhp it would be at 8,000rpm and your engine could peak 250hp at 3,500rpm and carry that power.
Or another way to say it is- at 3,500rpm the NA p-port would be making only 80rwhp.
Sounds like a crazy set-up and a wild ride!
You say that N/A power like it's a bad thing! If you're only at 3500 then it is because you're in a corner and you can't put much power down anyway.
The turbo is IIRC smaller than Turbo II unit. Probably will have to play a lot with exhaust housings since the Ford housings were also tiny, something like .48 or .63 A/R on a baby T3. Bear in mind that rotaries need a good deal more airflow than a piston engine to make the same power.
I like the placement of the PPorts doesn't look like you get as much overlap compared to how most PPorts are placed. Also how wide is the PPort a lot smaller than N/A's that I've seen. Nice to see something different and that works, not ideal but who cares it works.
This is a schematic of the boost sensor to modify the TPS.
The turbo I have has a A/R of 0.63. The exhaust size is 2" out. The supply air enters 1-1/2" copper to a plenum. From the throttle body the air divides into more copper that is also 1-1/2" and the runners are about 10" to the engine.
Yes the intake ports are much higher on the rotor housings. The shape inside is round and the direction is perpendicular to a tangent at that point. The OD of the copper sleeve is slightly more than 1-3/4". The hole saw was 1-3/4". Copper can be shaped/stretched so I had a very tight press fit when the coupling was installed. Of course they are sealed with an epoxy.
The timing of the intake opens later than a bridge port, but sooner than a large street port. Imagine the street port opened to the shape of the rotor housing....... Yes, past the corner seals.
The exhaust ports have the sleeve removed and have been race ported.
The engine idles at 1500 rpm. I established a base tune by wiring the wastgate open to have virtually no boost untill 5500 rpm. This engine runs very good this way although it is nothing spectacular. It is a little more powerful than a stock 4 port engine.
BTW this engine is basically a 1974 13B from an RX4 but has long tooth stationary gears. The rotor housings have the water jackets modified with grooves for cooling.
I have a unique coil to plug wasted spark set up for the leading ignition and use the distrubutor for only the trailing spark. 1980 electronic distributor......
My car weighs about 1900# with me in it. In my class I race against Lotus Seven clones that have late model Corvette engines. Also a factory race GT Fiero with a huge V-8 in it but our minimum weight is the same by the rules....
In looking at the Dyno graph, I would say my butt dyno reads very similar to that. I have a PTO dyno that I attach to the rear locked axle to test/tune while in second gear. It really twists the chassis hard ......
I put my 13B turbo and Logan's (defined) 20B NA semi-p-port when it was 420rwhp like my set-up in my torque at the wheels by speed calculator.
If I use my stock 2nd gear for auto-x speeds and give the NA 20B an aftermarket gear set with optimal/available 2.48 1st gear here are some rear wheel torques at auto-x speed.
29mph
13BT 3,200rpm= 2,809ft/bs
20B NA 4,000rpm= 1,967ft/lbs
36mph
13BT 4,000rpm= 3,304ft/lbs
20B NA 4,900rpm= 1,816ft/lbs
43mph
13BT 4,800rpm= 3,305ft/lbs
20B NA 5,800rpm= 2,237ft/lbs
50mph
13BT 5,600rpm= 2,974ft/lbs
20B NA 6,800rpm= 2,339ft/lbs
57mph
13BT 6,300rpm= 2,809ft/lbs
20B NA 7,700rpm= 2,390ft/lbs
64mph
13BT 7,100rpm= 2,479ft/lbs
20B NA 8,700rpm= 2,440ft/lbs
71mph
13BT 7,900rpm= 2,065ft/lbs
20B NA 9,600rpm= 2,135ft/lbs
And of course the 13BT set-up will cost 1/2 to 1/4 the price of the 20B NA/gearset and be all off the shelf parts.
20B NA car would get to weigh 100lbs less (5% of vehicle weight) though (from calculated displacement) and can brag it makes more torque at the wheels- edit- I mean can brag it makes more torque at 71mph.
-Edit edit- Looked again and 20B NA car could use RX-8 gearbox and 4.77 rear and use the 2.269 2nd gear would work to 69mph for cheap.
Calculating speeds off 25" tall tires (295/30-18).
This is fun.
Check this 493rwhp 6.0L LS2 (CNC Trickflow heads, cam/valvetrain, intake/exhaust) using Fbody T56 2nd and 3.9 rear.
29mph
13BT 3,200rpm= 2,809ft/bs
Built LS2 2,700rpm= 2,638ft/lbs (had to extrapolate 380ft/lbs chart starts at 3,300rpm)
36mph
13BT 4,000rpm= 3,304ft/lbs
Built LS2 3,400rpm= 2,777ft/lbs
43mph
13BT 4,800rpm= 3,305ft/lbs
Built LS2 4,000rpm= 2,800ft/lbs
50mph
13BT 5,600rpm= 2,974ft/lbs
Built LS2 4,700rpm= 3,110ft/lbs
57mph
13BT 6,300rpm= 2,809ft/lbs
Built LS2 5,300rpm= 3,110ft/lbs
64mph
13BT 7,100rpm= 2,479ft/lbs
Built LS2 6,000rpm= 2,950ft/lbs
71mph
13BT 7,900rpm= 2,065ft/lbs
Built LS2 6,600rpm= 2,603ft/lbs
Where is that V8 low end torque?
Its in the displacement!
Here is a built 609rwhp built 7.0L LS7 (headwork, cams/valvetrain, intake manifold/TB, intake/exhaust). Using Fbody T56, but 4.1 rear to help torque because of higher redline.
29mph
13BT 3,200rpm= 2,809ft/bs
Built LS7 2,800rpm= 3,065ft/lbs
36mph
13BT 4,000rpm= 3,304ft/lbs
Built LS7 3,500rpm= 3,284ft/lbs
43mph
13BT 4,800rpm= 3,305ft/lbs
Built LS7 4,200rpm= 3,795ft/lbs
50mph
13BT 5,600rpm= 2,974ft/lbs
Built LS7 4,900rpm= 4,014ft/lbs
57mph
13BT 6,300rpm= 2,809ft/lbs
Built LS7 5,600rpm= 3,941ft/lbs
64mph
13BT 7,100rpm= 2,479ft/lbs
Built LS7 6,300rpm= 3,649ft/lbs
71mph
13BT 7,900rpm= 2,065ft/lbs
Built LS7 7,000rpm= 3,211ft/lbs
Time for a EFR 8374 and some porting if built LS7 are in your racing class...
You can see why in NASA racing turbo 2 rotor is the way to go since they class by actual hp and but then give rotaries a handicap because everyone knows they make no low end torque...
I am not too familiar with NASA rules and I am building to SCCA E-Mod rules. I did lightly breeze through the NASA rules to get a basic idea of what you are saying.
The comparisons shown here are amazing to me. The things I see that are most relative to me are:
...Any of the turbo chargers including my old airesearch unit will make amazing power. I will get enough power to get me to a competitive level. I was really suprised how fast the largest turbo would spool!
...The new BorgWarner EFR units all seem to offer a wide use range as well as easy fast spool up. One neat feature is a built in blow off / recirculating system to be more compatible with MAF sensors.
...My fuel system as I said is pure alpha-n that reads TPS, RPM, and coolant temperature. From there the tuning unit is just a volume and tone control for the fuel injectors. Fuel pressure and injector size are unknown to the fuel controller. I added the Boost-TPS sensor shown above to keep from going lean going from vacuum to boost.
Before thinking about a matching or upgrade in my turbo, I need to solve the issue of the engine not letting go once into boost in order to stop or even slow down. Even the largest turbo represented here would have potential to keep feeding the fuel at 1/4 TPS with latent air pressure if the bypass/blow off will not release the device shown above.
Turbochargers cost money and more fabrication time.
Fuel control systems cost money too and will require more sensors even if it is a MegaSquirt.
I used this turbo and fuel system on an engine that was a 4 port half baby bridgeport engine. The 2 barrel throttle body was adapted to the factory RX4 manifold with a 2" thick casting. I limited the boost to 5 psi to be very conservative. I did not need to advance the TPS signal to transition from vacuum to boost like I need to do now. I think maybe this Pport engine has a lot less restriction in the intake runners.
How effective is a blow off valve for releasing the latent air pressure when the throttle plates close?
Before thinking about a matching or upgrade in my turbo, I need to solve the issue of the engine not letting go once into boost in order to stop or even slow down.
How effective is a blow off valve for releasing the latent air pressure when the throttle plates close?
I believe your issue may be partially due to the p-port.
I had similar issues with just extreme street porting and a small turbo- that is, no matter how little throttle I gave it the motor responded with near full boost/power.
Power was basically directly related to turbo shaft speed and I wasn't able to throttle that as the turbo was so small/responsive.
I fixed it by making my ports very conservative and increasing the turbo exhaust housing flow.
I never noticed a difference with blow off valve or not regarding this problem on my engines.
Or does your motor even produce power with the throttle completely closed after having been open?
Or does your motor even produce power with the throttle completely closed after having been open?
Once the turbo boost dissipates its pressure, after WOT, the engine will drive me back to the pits without spooling the turbo at small throttle opening. The boost is does not come on instantly if I am not asking for small acceleration at just off idle .
If you look at the schematic you can see where the TPS acts normally from foot feed and how it is changed as boost increases. I need to make the boost side of this gadget let go when I let go of the throttle. The blow off valve is supposed to open when the engine has vacuum and there is pressure in the intake plenum. I am curious to how much pressure the blow off valve will release.
I guess I will have to wait till the snow is gone to try the blow off valve.
Your throttle plates are mechanical and either open or closed.
Your TPS is controlling your fuel.
Fuel + exhaust heat+ air from port overlap = combustion in the exhaust manifold spooling the turbo.
Air is getting into the motor/exhaust through whatever small gap/passage you have to allow the motor to idle, Since it is still boosting more air goes into your engine than you would think to feed the exhaust and keep the turbo spooled.
Yes, finding a way to cut or lean out fuel at low TPS input will slow the turbo.
Yes, opening a BOV will lower boost at the throttle body and slow the turbo.
Another solution is to put the throttle plate in front of the turbo (which will increase lag at low throttle opening as well).
Another solution would be to throttle the exhaust. If exhaust can't easily exit the turbo the turbo shaft speed will also slow.
Your set-up really goes back to the early days of turbo charging and you can see the solutions they used back then.
The boost is does not come on instantly if I am not asking for small acceleration at just off idle .
Yes, yes. I should have been more clear.
In the rpm range where the turbo could make full boost and was very responsive (4,000rpm-8,000rpm on my set-up) any amount of throttle resulted in near full power on my aggressive street port set-up. It drove fine in low rpm lag.
12-25-16, 02:16 PM
