3 years ago we built an FD3S Rx7 for a local customer who wanted to make 400rwhp. We built the car from head to toe, including one of our EFR IWG 7670 turbo systems, and a small street-port. The car made 396rwhp and 361rwtq at 20 psi ramping down to 15.5 psi at redline . This was on an E55 flex fuel tune with an Adaptronic E440D wire in model ecu. See that video here. This was plenty of power for the customer at that moment in time, and at the limits of the walbro 460lph drop in fuel pump. 3 years pass and the customer decides he wants more power, so we decide to try out the newer EFR 9174 IWG turbocharger. Moving up in turbo size is literally a bolt in installation with changing the intercooler and intake pipe couplers. We did update the ECU to an Adaptronic M1200 modular ecu, and quickly did another dyno tune to make sure the dyno comparison would be as accurate as possible.
It only took us 5 passes to tune the new turbo thanks to the modular ecu( all the way to 27 psi!). Below you can see the overlay. As to be expected the EFR 7670 makes a lot more power down low, and the EFR 9174 makes a lot more power up top. The EFR 9174 is running more boost pressure in the midrange, and top end, where as the EFR 7670 is running more boost pressure down low. The EFR 7670 can make 30 psi by 3k rpms, where as the EFR 9174 can only make about 12-14 psi at 3k rpms on this combination. Keep in mind that even better response can be yielded on both with 3.5" or bigger exhaust systems. This car has a full 3" exhaust which is the most common option. The EFR 9174 could definitely benefit on the top end with a 3.5" exhaust at these boost pressures, as we recently saw a 40 rwhp power gain on another car above 6k RPMS( large streetport at 20psi making 490rwhp). Keep in mind that a full 3.5" exhaust on this size of a turbo( 9174 or bigger) in IWG form will not be able to keep boost pressures under 17 psi.
At 3000 RPMS the EFR 7670 makes 300rwtq, and the EFR 9174 makes 140rwtq. The 7670 is at 18 psi, where the 9174 is at 12psi.
At 3500 RPMS the EFR 7670 makes 347rwtq @ 18.5 psi & 365rwtq at 21.5 psi. It will also make 400rwtq @ 30psi( not shown below).
At 3500 RPMS the EFR 9174 makes a max of 20 psi and 307rwtq. This is roughly 60rwtq less than the 7670.
Clearly the EFR 7670 has the edge below 3500rpms.
Below we increase the bottom end even more with the EFR 7670 to show max response and low end power( dyno sheet below).
At 2800rpms we increase boost pressure to 20 psi making 345rwtq @ 3000RPMS( up from 14 psi and 300rwtq @ 3k rpms above)! The EFR 9174 is only at 232rwtq @ 10 psi( it cannot make any more boost at this RPM).
Here we have a 113rwtq difference between each turbos, and that is a massive difference for those looking to do AutoX, or primarily drive on the street. Especially if one is limited to pump gas where the bigger turbo really starts to shine at high boost.
At 4000RPMS is where both turbos equalize in power. Keep in mind that the EFR 7670 is able to make a little bit more power than show at 4000rpms. Above its making 20 psi, and it can max out at 25 psi here. One is able to run 25 psi to about 5500rpms, and maintain a flat torque curve of 400rwtq from 3500 RPMS to 5500RPMS. After 5500 RPMS the torque will start to drop as show in the above sheet. Engine porting does affect this, as this small street-port we did is geared more towards response and street ability ( low/mid range power, vs top end power).At the current boost pressures, 20psi on the EFR 7670 VS 27 on the EFR 9174 the 9174 is winning. As previously mentioned this would be closer at 25 psi on the EFR 7670.
We do have more dyno charts on our website for different engine porting combinations. Both turbos will make more peak rwhp with engine porting at a slight cost to response. The bigger the turbo, the bigger the difference.
At 4500rpms the EFR 9174 clearly wins, and can win by a mile here at 30+ psi( 27 psi shown). The EFR 7670 cannot make 30+ psi at this RPM; its out of breath. The above dyno runs show the sweet spots for both turbocharges, that is why we picked these boost pressures. At 4500rpms the EFR 7670 is at 300RWHP, and the 9174 is at 375RWHP.
If you look closely you will notice the shape of the torque curve is very similar, its just shifted to the right on the EFR 9174, which therefore will make a lot more peak RWHP. At 24 psi the 9174 is making 522rwhp at only 6800rpms. Unfortunately the clutch was starting to slip and we couldnt see the peak numbers. Its probably pretty close to 550rwhp on this dynojet with a twin-disk.
We will revisit this again in the future, with more sizes, and hold each turbo at the same boost pressure etc. However its Spring time here, and we cannot spend all day playing around on the dyno.