Is this the setup that's on your EFR turbo setup page, dyno graph there?

Where it isn't full torque until 4400? It seems a stretch to compare that to stock twins which hit a peak torque at 3200.

 

Where it isn't full torque until 4400? It seems a stretch to compare that to stock twins which hit a peak torque at 3200.

Yeah, 390ftlbs at 4,400rpm.

only 315ftlbs at 3,200rpm.

Well, you would rather have ~220ftlbs at 3,200rpm with a 350-400rwhp stock sequential set up?

Reminds me of a friend I have that says cars with equal torque to hp make great torque. No.... it means they don't make crap for torque past 5,200rpm.

Anyone would rather have a car with 300ftlbs torque and 400hp than one with 300ftlbs torque and 300hp, but he hasn't grasped this concept yet either.

Anyways... the EFR76 is what should be compared to stock turbos as the peak hp number will be the same.

 

What part of 'response' are you not getting here? You know it's different than 'more power better' right?

 

He's saying that even though it's not making peak torque at 3200 rpms, it's till making more tq at 3200 than the twins would so its irrelevant.

 

That's not true necessarily in autocross. Being able to spool early and quick is more important than riding a curve of torque growth. Here's an example /AUTOCROSS/ dyno chart:



See the 250 ft/lb at 3000 rpm? See peak torque at about 3600? When that happens matters a lot in this kind of racing. Every bit of when peak torque is hit means a huge change in the transitional behavior of the turbo in rolling out of corners.

So, again. Response is this thread. There are a thousand 'how do u get most hp from rx7' threads out there, this just isn't that.

 

^
And you know the guy that chart belongs to is making changes right? Be careful of what you think you know.

 

I agree about the importance of response versus outright numbers at any given rpm.

Transitional response cannot be shown on the dyno sheet so we are guessing how these setups "respond" to gas pedal input without owning and driving them ourselves.

I own a sequential FD and a single turbo FC that I will be putting an EFR 7670 in, so someday I will have some feedback I can present on that.

I can say that in exhaust chocked rotaries like tiny primary turbo on FD or much worse a S4 with the primary 0.4AR scroll the boost response IS great.

The torque response *can* be great, but often the exhaust chocked engine is operating in a lower VE range so the torque response suffers.

On a sequential FD this can CLEARLY be felt with a full stock exhaust versus a very open one.

Both spool fast, but a well developed bolt on sequential almost has too much torque response. Not that you really can ever have too much, its just takes more skill and a race seat/4 point to drive smoothly.

Yes, we all do want a single turbo like that!

 

Like I said the 7640 is going to spool very much like the stock twins, I have not personally rode in speedjunkies seven but running next to him you can here him start seriously spooling at just over the 2000 rpm range. Both my wife and a very good friend have as they both wanted to see what his felt like vs my FC with a bigger turbo putting out more top end. If I kept mine above 4k I was faster if I let it drop down below that his transient and earlier full boost would let him pull till I got to about the 6k range.

 

I have been in a efr7670 fd. The car rips. The stock twins are not like it. They are much slower and spool slower with slower response. Just mo.

 

https://www.rx7club.com/single-turbo...sults-1070794/

Just cross posting my EFR 7670 results as there was so much discussion of that turbo in this thread.

In the linked thread I do have a short video of response in 5th gear, 4th gear, 3rd gear and back to 5th.

By the dynojet #s in the thread that is 175hp @ 3,000rpm or

300ft/lbs torque @ 3,000rpm

And then with the 7670 boost keeps climbing from 19psi to 26psi for a bit more torque after 3,000rpm (looks like it peaks around 375ft/lbs).

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Cliff notes-

Stock sequential can boost more between 1,000-2,000rpm (and thus make more torque in that range).

EFR is equal to the very best set up sequential twins or ahead of 99% of sequential twins by 3,000rpm and then can make more boost (torque) after that.

Honestly, I would still take the twins for a street car that will never see E85 or race gas.

For the track where exhaust heat is a problem I think the EFR 7670 is going to be about the smallest hotside/most responsive turbo you can reliably run.

For auto-x- we shall see. So far I think the EFR 7670 is going to be ahead of sequential twins from the ease of driveability standpoint. No switchover and better boost recirc off throttle for better part throttle driveability.

Despite the early torque it drives like it has really good traction/recovery.