C. Ludwig

The 7670 is making good numbers but it's being abused to do so. With the responsiveness of the 8374 being similar, I see no reason to run the 7670 and ask it to run outside of its efficiency range. The 8374 will do everything the 7670 will, and more, and be happier doing it.

If this car had the supporting components to hold steady boost, the results would have been even more impressive.

Well, you have to size the turbo to the racing application, not the dyno.

I just watched a vid of my FC on 7670 on a kart track I auto-x at where it was dark enough I could clearly see the peak hold light on the boost gauge that comes on at 2 bar or 28psi.

It was only illuminated about 12seconds of the 49 second lap and I could hear I am giving the car throttle at least 24 seconds a lap.

Tells me I actually need a smaller turbo for this track so I can be at full boost more than 50% of the time I request it.

It also tells me I need a data logger so I'm not watching videos and counting! LOL

 

Fortunately, for myself at least, I have proper logs of the 7670 being driven on the street. It's in overspeed conditions with a stock port engine. Having said that, I've been part of a very successful racing campaign that involved a terribly undersized turbo. That turbo worked well for that specific application on course and it lived a relatively very short life. I'd never put that combination on a street car. So there are situations where conventional wisdom does not apply. However, making broad strokes and saying the 7670 is a properly sized compressor, especially in anything that's been ported, is probably not accurate.

 

At what boost levels?

 

All of them. Lower pressure ratios actually worse than higher, if that's what you're getting at. https://www.rx7club.com/single-turbo...esuts-1088491/

 

Well I'll be jiggered. I have a 7670 going on my (mainly) street car soon! Only planning to run perhaps 16psi maximum.

 

C. Ludwig

Fortunately, for myself at least, I have proper logs of the 7670 being driven on the street. It's in overspeed conditions with a stock port engine.

Holy crap, the 7670 is turning more than 140,000rpm on the street?

I did not catch that from the last thread you are referencing. I thought you were just saying it was not running through the peak efficiency islands of the compressor map...

 

Ditto.

 

That's what I've been saying.

The pressure ratios are a bit off since we're missing a couple measurements and relying on only manifold pressure. But the speed measurement is accurate.

 

Hmmn, I see that you plotted for 20psi boost (2.5-ish PR) at 8,000rpm and on the 123,300rpm turbo speed line for the 7670.

So, you are saying IF we managed to get the 7670 to boost more than 20psi at 8,000rpm it would be jumping up to the 140,000rpm speed line or above and shortening the turbo life.

So you did or didn't see over 140,000rpm on the turbo speed sensor?

 

Hahaha. I need to stop posting... You're correct. Not over speeding, just way off the right side of the efficiency range.

 

Gotcha!

That is what I did get from your earlier posts in that thread.

7670 is operating out of its peak efficiency range on a rotary at any boost under 20psi up to 5,000rpm and it is out of its efficiency range at any boost level after 5,000rpm.

Hahaha. I need to stop posting...

We appreciate your contribution to the forum!

 

Phew.... inefficiency I can deal with given the huuuuge core on the Greddy Vmount I have, but I really didnt want to be reducing the life of the turbo through overspeeding

 

FWIW, when i bought my EFR9180 Borg Warner sent me gratis a speed sensor w the comment, do not run it over 116,000.

the concern was separation of the joint of the two piece turbine wheel/main shaft.

Matchbot calculates it take around 100 HP to drive the compressor.

the combo of a joint that:

needs to hold 100 hp
is of dissimilar metals
must function at very high temps
can spin at 100,000 rpm

could be a challenge.

make no mistake about it, the aftermarket (that's us) sole function is to
deliver a lower stakes R&D result for OE.

since the 7670 has a tiny hotside wheel (5.23 average sq inches V the 9180 at 7.19) as well as significantly less power perhaps it isn't an issue.

My ViPEC V88 has a digital input for turbo speed but it has a limit of 500 hz. the BW sensor divides RPM into hz and then by 8 so i built a module to divide the signal by another 8 and will be using it on my SXE turbos as well as my 9180.

 

Only the 9180 needs to be watched super close for overspeeding and shaft separation.