Luke

I HAVE A #6 hot side, And I didn't even mention 'mass' yet. Mass has very little to do, since the recipricating mass spins 100k rpms.

i'm talking about the actually act of compressing air. ( what a compressor wheel does <img border="0" title="" alt="[Wink]" src="wink.gif" /> )

TonyG

So how laggy is your 60-1HiFi/#6 hot side (and which exhaust trim do you have?).

I drove one, and it spooled real fast, but the top rolled over at 6k.

Tell us how bad it spools....

fast951

The turbine wheel converts exhaust enery into work. The efficiency of wheel dictates how well the job gets done. If the turbine wheel is smal and its efficiency is at a mismatch with the compressor wheel you will have lag.

If you think about wheel efficiency, vs size, you might get better results.

Let's look at a K26 hot housing, mated to a large compressor. The K26 turns quickly and is efficient at a certain RPM. If the compressor wheel has a different efficiency (RPM mismatch), you will have lag. By the time you get to the compressor efficiency map (where you are generating boost), the turbine is in a very inefficient area.

Size and weight affect lag. However not as much as a mismatched turbine/compressor efficiency.

Luke

how does one dictate turbine wheel efficiency. and efficiencies should match at turbine speeds? or (pressure ratio/rpm)

fast951

Turbine maps are hard to obtain so most people just look at the compressor map. The goal is to obtain the highest efficiency on both sides of the turbo at similar (close enough) speed.

Also keep in mind, that the housing plays a big role as well. A #10 with a Stage III wheel behaves differently that a #8 with the same wheel.

Many variables to account for. Also, even if the numbers look good. Nothing can replace actual testing and experimenting.

J Chen

Hi Tony,
When you speak of 60-1 with #6 hot housing, are
you refering to the KKK #6 hot housing & also
how quick does it spool up & what kind of hp
will it produce running at 15-18psi.
Thanks

keith

I'm lurking, of course (STILL with a K26/6...)

Luke

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by J Chen:
<strong>Hi Tony,
When you speak of 60-1 with #6 hot housing, are
you refering to the KKK #6 hot housing & also
how quick does it spool up & what kind of hp
will it produce running at 15-18psi.
Thanks</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">i' saw full boost at about 3800rpm, i'm not so sure my a/f was decent as he swapped sensors the next week. I can't comment on powre either.

TonyG

I think Luke answered this question.

Full boost at 3800 rpms is sooner than a stock turbo S turbo, and hence the argument ends...

You can make a 60-1 HiFi spool quickly and they are not only good for top end power, etc...

With the same 60-1HiFi compressor and my Garrett hot side, I get full boost at about 4300rpms.

That's 500 rpms later than Luke's setup with the same 60-1HiFi compressor. Like I said... you can pretty much control what the compressor will do with the sizing of the turbine side of the turbo.

Luke: Where are your dyno sheets?

Bri Bro

I would give SFR a call. They are not cheap but Tim has a lot of experience in this subject. I would say you can make your goal of 350HPRW with the correct injectors, chips and MAP/MAF controller.

Read Maximum Boost page 31-33 for more information on how A/R and Turbine size effect performance.

J Chen

Hi Guys,
Thanks for the advice. Hey Luke, are you running
the #6 or #8 hot housing ?

fast951

The #6 with the 60-1 is very restrictive.

TonyG

#6 hot side will be fine with a stock cam and stock exhaust ports.

Yes it will be restrictive, but no more than a stock turbo or stock turbo S exhaust port to turbo setup. Your peak HP will be at 6000 rpms... so what?

You can make 340 or so HP to the wheels without any problems using the #6 hot side (using a K27 compressor!).

fast951

TonyG,

Have you checked the backpressure on the setup you are recommending? In your opinion what's an ideal Backpressure ratio (exhaust to Intake pressure ratio)?
What is the ratio that makes engine management (due to knock) out of control?

The stock K26 compressor flows less air than the 60-1. Of course the #6 will not be restrictive when use dwith the K26. Why do you think the factory used the #8 on the 951S...

Why do you think the K27#8 makes more HP than the K27#6? Same K27 compressor...

TonyG

I've not checked the back pressure on my setup. The exhaust side (and the compressor side) was specified by John Milledge to work with the head/cam/valvetrain that he provided.

I've got the provisions to do so though, and will be doing so once I'm finished adding the new intercooler.

At that point I will possibly be changing the turbo, and will use the dyno sheets as well as the back pressure (as well as boost pressure) to determine which way I want to make the final modification.

The "ideal" pressure ratio was provided to me by John Milledge which he asked me not to disclose (along with some of the cam specifications and the photos of the exhaust port work). Is his ideal pressure ratio the best? Who knows!

...

Nobody ever said that the #6 side isn't restrictive. But it does work, and it works pretty damn good on a mildly modified street car for sure.

I've seen (and have owned) these turbos and really like them a lot for the street (even for the track). They just cannot provide the power above the 330-350 mark that I'm looking for.

If I had a stock or very near stock street car it would be the turbo I would install again for sure.

And I agree, once again, that the back pressure costs power, but it only does so at the limit. Making 325HP isn't the limit. 345 is on a KKK #6 hot side.

As with everything, it's a trade-off. Bigger hot side, more lag, more top end. Smaller hot side, less lag, less top end.

And yes the K27/8 will make more top end power than the K27/6, but have you ever driven a car with a K27/8 turbo? It sucks. Way too much lag in light of the fact that the compressor isn't going to every make big top end numbers. The K27/6 on the otherhand spools awesome, and will pull and make power to 6000 rpms.

The K27/8 will allow you to make more top end power, but at the big expense of turbo spool (a good 600+ rpms later).