I ran my 7670 on a 7 psi turbosmart spring and couldn't get it past 8 psi on a 4th gear redline pull.

that's with a 3.5" downpipe, and a small shorty filter. stock port with 9.7 rotors.

 

7670 with a 3.5 inch full exhaust on E85 held 8 psi to redline with 9.4 rotors..

 

Any idea what power it made?

 

Around 300rwhp I believe.

 

For those not aware we make a top mount IWG EFR system for the REW swaps in the Rx8. These are very popular.

Here is one that made 330rwhp @ 11psi on pump gas. Full 3" exhaust.

https://www.instagram.com/p/BDIuOoUQ...en-by=turblown

 

What's the power potential difference between the 7670 and 8374 on 91 octane, all else equal? You said the 7670 can hit 440whp on 91, haven't seen a max effort 8374 on 91.

 

I think it's safe to say around the same combustion chamber pressures regardless of which turbo is making the positive pressure when speaking in terms of equal Intake temps, 91 octane etc. pressure is pressure.

I wouldn't engineer a set up for the ragged edge of 91 Octane anyway. Seems like a recipe for a short lived motor. For the cost of water injection kits these days it seems somewhat a ridiculous notion to push the envelop on just straight pump without some form of AI.

Cost of a broken motor > Cost of an AI setup.

 

Does full exhaust like midpipe or resonated midpipe really makes that much of hp difference than hi flow cat? i need some help with my numbers to figure out if it's my exhaust or something else? I have ur mani & downpipe, 8374 turbo iwg, SMB hi flow cat with muffer and RB catback, i only made 356 rwhp with 17 psi. stock ports, no ignition break up, and 9's sparkplug with hks twin power plus running meth injection, and power fc.

 

Khris, who was tuning the car? I'd actually love to check your car out and get a ride this weekend or next, would be pretty cool to compare power bands and setups

To answer your question, a HFC will certainly hurt power, as will certain restrictive catbacks.

Hell, I recently switched out from a resonated MP and RE-A dolphin catback to a different larger diameter resonated MP and freer-flowing catback and picked up boost and power, a fair amount from the feel of it

 

What dyno? You have been around long enough to know Dyno's all read differently. Also a better indication of power would be a trap speed. You could always take it to the track and get a 1/4 mile MPH or if that's not your thing get a Vbox and use that. You can compare notes with other owners and slips and see where you are.
It's quite possible you can was tuned extremely conservatively. Or God forbid your motor is low on compression. You can get a compression test, buy your own tester or take it to IR Performance and have them use their rotary compression tester.

 

As mentioned what brand of dyno? A dyno dynamics in standard mode reads %15 lower than a dynojet.


I did a back to back on a 7670 with and without the cat, and it was 33rwhp on the top end.

There are a ton of variables, but lets see the dyno chart.

 

^Elliot, what boost level was that back to back at?

 

I will need to go back to finalize more tuning, if i decide to removed the cat smell like fumes!

 

The torque curve is nice and flat at least, but I always hate seeing a dyno graph with different scales for HP and TQ. makes it appear that the torque is higher than it is.

 

The dyno sheet says 15psi for each run? Is this wrong?

I assume this is wrong. pull 15 in green is at 15psi and runs 21/22 are 17 psi?

Based on the difference in AFR between the pulls( low to mid 11s for run 15, and 10.6 to 10.3 for runs 21/22) I assume this is because of the increased boost pressure.

Notice pull 22 is pretty wavy up top, and this is with smoothing set to the 5( MAX).

Also notice how close the torque and HP on pull 22( 356rwhp to 313rwtq). This indicates a flow issue in the higher rpms.

I am sure you are aware Peter Hahn made 430rwhp on this same turbo kit, and same dyno at 15psi( pump gas). So we can rule out the dyno reading low completely.

Take the cat off, and while you are it throw some real plugs in there( NGK R7420-9s).

Tune seems awfully on the safe side with meth injection( 10.6 and lower)

 

When I swapped from a GT3574R to an EFR 8374 IWG, I gained power down low and up top at max rpm. the car feels a lot better. it also delivers power more smoothly. I have a 3.5" downpipe, 3" magnaflow resonated midpipe and 3" amuse R1 exhaust.

I also notice the car likes richer fuel mixture, leaving the boost controller (powerfc) at the same level if I add a little more fuel 11.5 afr vrs. 10.5 afr, the 10.5 has lower knock, more boost (slightly) and overall feels better and healthier. so I left the tune on the rich side as it seems to like it.

Peak power wise the two turbo's are close at 15PSI. the 8374 makes more above this, 6,000ft above sea level.

I think the GT3574R feels faster, but the efr 8374 is faster. the turbo delivers power soo smoothly and easily, the only thing I do notice is the 8374 does not like to go to redline under partial boost levels, seems like the turbo surges or kicks you out of that area. not really a big downfall as you would rarely be doing this but something I noticed, didn't do this with the GT3574R.

 

I think that is because the EFR turbo is so much lighter and more efficient that part throttle boost becomes an issue. I know for a fact that on my Dodge SRT-4, if I run a MBC then it surges like crazy and spools at part throttle. Even as low as 2000 rpm. It's because the turbo is so darn tiny, so Dodge used a 3 port solenoid to keep the turbo offline to avoid surging unless you are at or near WOT. Even still, I get 18 psi at 2000 rpm with the stock turbo, so the response is amazing, but it shows how tiny it is with the surging. I took the MBC off and kept it at factory control

 

ACR_RX-7


I think that is because the EFR turbo is so much lighter and more efficient that part throttle boost becomes an issue.

If this part throttle issue is with all EFR 8374 it could be compressor surge I guess.

I'm thinking it is a tuning issue. If you can get to a loading dyno like a Dyno Dynamics or Dyna Pack you can set the RPM hold and work through all load ranges to get clean AFRs in each RPM range.

This really helped my TII back when I had the old 60-1. I used to have to short shift 1st and 2nd or it would spin or buck at high rpm like you are describing, but once I got a good tune it was smooth.

------------

I didn't have that bucking at all with my EFR 7670 and it had crazy response.

In fact, I was super impressed with the EFR 7670 because I could really dial in whatever torque/boost I wanted with the throttle pedal. It was like there was a direct connection between the throttle pedal and the boost gauge needle.

With EFR 7670 I could just give it baby throttle and drive around smoothly at any rpm/boost. If I got a little randy with the throttle it would instantly spin the tires.

 

Less-gradual(narrow) power delivery does indeed 'feel' faster.
https://en.wikipedia.org/wiki/Jerk_(physics)
It's why turbo's are so much fun, in general, compared to N/A engines.

 

^ I disagree with that. To me the big downfall of a turbo engine is the nothing nothing wham thing.
Which is a novelty at first maybe but after that its a pain in the **** and a hindrance.

 

as if all turbo engines are created equally.. sounds like you only have experiences with shitty turbo setups and never a proper one. like a journal bearing gt45 on a 2 rotor.

lag depends on the turbo the engine and the desired goal.
wanting to use a 2.0 4 cyl to make 900hp is unrealistic, yes people still do it but then you get no power until 6k rpm with the turbo finally spools
on the other hand you could use a boosted ls1 to make 900 and IF proparely sized will spool low in the rpm for a broad power band.

the simple fact is going from our 1.3 rotary to any thing bigger is outside most peoples budget as the only thing bigger is the 3 or 4 rotor. this means we get pushed in to a state of putting too big of turbos on too small of en engine...

that's why sequential 7670 is the hot ticket.

 

I'm still waiting for someone to get around to a twin EFR setup. The idea has been thrown around for awhile, but alas, I am unable to afford such adventures.

 

Thanks for that professor.

 

But its true, most people really love the no power then boost and big power feel of a laggy turbo. I mean, how else do they know the turbo is doing anything?

Honda used to tune its VTEC so torque dropped off on the primary cam before the VTEC cam comes on (too late of switchover) so you can feel that VTEC kick. How else does the consumer know they are getting anything with VTEC?

I had plenty of years driving a TURBO car (lag) so I really appreciate an engine that has a broad torque band that includes the rpm range I cruise in (2,500rpm-3,500rpm in RX-7 gearing).

I don't care it it doesn't have 300ftbs torque from idle-2,000rpm like an LS V8 since you can't put that through the tires anyways in 1st gear.

As long as it has enough torque to spin drag radials on a prepped track through 1st without having to abuse the clutch by revving the engine up much over 2,000rpm I am happy.

Oh, and I want to be able to granny shift and still be fast. I am over the whole having to get everything perfect on launch and power shifting each gear to get a decent time.

 

Ideally you fix this by using a decent BOV, like the synapse item for example. ideally one dials it in so it just not open at maximum airflow under wot conditions. , lets say 100 mbar delta which you could or not get with a littlebit restictive throttle

then if you cruise with lets say atm pressure in intake, the bov will open at approx 1.5 psi boost upstream throttle and avoid turbo from surging.

even if zou generally increae load the bov will adjust the boost upstream throttle plate to a fixed value ( +- 100mbar) and avoid surging and unneccesary pumping losses and thus also improves mileage