eastendr

While I'm (patiently) waiting for Danno's MAP 2 upgrade , I'm sourcing a new turbo.

I currently have a K26/8 (car is Turbo-S spec). I also have a 3" no cat stainless exhaust, LR DPW, Blitx SBC-iD boost controller, Dump valve, adjustable FPR, MSD etc.

I have a set of #55 injectors and a LR stage II Intercooler waiting to be fitted when the vented badge panel's sprayed.

I'm now looking at the turbo. I've been following a previous thread, with TonyG commenting and comparing the K27/6 & K27/8, and think this is probably the best way to go for me, as I want to retain the water cooling and not have to do too much chopping about.

I can get the turbo built for me here in UK from new components, so here's the question - K27/6 or K27/8 ?

K27/6. I know that this is highly recommended with very fast spool up. I know that this can cause a boost spike, but that the SBC should be fast enough to tame it.

K27/8. More lag, but worth an extra 15 RWHP.

If the K27/6 spools faster than the K26/8, how does the Spool time of K27/8 vs K26/8 compare ?

I can accept lag (as I'm used to a T04E on an RS 500 running 36 PSI, boost not coming in until about 4,000) if the mid and top range power is that much stronger, although the car is 90% for road use.

What is the recommended max boost with this setup (#55 injectors) ?

What anticipated RWHP with all the above in place ?

Would you raise the rev limit slightly with the bigger turbo, but standard, good condition bottom end ?

Over to you gentlemen ....

Rick

TonyG

If you look at the thread that you mentioned, you'll see a dyno chart.

That's what you can expect.

The only reason you'd have a boost spike is if you don't have a good wastegate and boost controller.

Also, I would think that the #8 hot side is good for more around 10RWHP. The additional lag isn't worth it the reduced "area under the curve", not to mention the lag.

eastendr

So you're saying stick with the /6, 10 rwhp potential, and the SBC-iD with DPW is fast enough to tame the boost.

Your dyno run was at 17 PSI, will the /6 flow more than that ?

Rick.

2+2

I also followed that thread and there appears to be a difference in opinion. Tony is very knowledgable about 951s and he recommends the 6 hot side. However, there was another person who held contrary views. I believe it was Crazyracer toward the end of the thread who claims that he has had both 6 and 8 hotside K27s and says that the lag is not that much different than stock for the 8 hotside. He also stated that if you are going through all the trouble, do the 8 hotside....apparently, at slightly higher boost levels, there is a big difference...I believe he said about 30 rwhp....the 8 hotside allowing you to run the higher boost....
All very interesting........

2+2

Ooops, that was misattributed. The person was blitz951 who stated:

"There is nothing wrong with a K27/6 but if your going to go through the hassle of changing turbo's then make it worth your while. I did not notice a significant difference with the #6 hot side and neither have any of my other friends who made the change. It spools up a little sooner than the #8 but so what because a split second later that #8 hot side will run away from your #6. The difference in power is like 30HP and it is noticeable. A car that you run side by side with with the #6 hot side you will pull away from with the #8. When you start turning up the boost then you'll see just how inefficient the #6 is. The #8 can go to about 21psi from what we saw on the dyno with a friends car(with race gas) and if you want more then you'll have to go with a Garret which is more efficient but if not and your on the street I would go with the #8. There are those like TonyG who made impressive power with the #6 but I dont know how and think that was an exception.
There is also another argument that the #6 runs good in the powerband range of the 951 engine and it is a good argument on paper but that hasn't been my experience driving the car.
Bottom line, head to head all things being equal the a car with the #6 will be slightly ahead to 60MPH but after that it will start falling behind in a hurry. I think Danno has some dyno's on this subject so maybe he can show us if he reads this. This has been my personal experience."

Good luck.......

Pheedbak

ohhh another UK based person with mucho car upgrades all good Im in Reading meself and id be interested to hear how u get on with the turbo upgrade as i think my turbo might need at least some TLC soon anyhow hope things go ok with the upgrade i have no insight to offer but good luck !

Do you get your turbo work done locally ??

Phil

eastendr

Look what I've started now

I'm still tempted more by the better potential of the K27/8 particularly if I want to go to even bigger HP later.

Tony, are you running a T04e now? and are you still on 2.5l ?

I note your comments about the greater lag, but the much stronger mid and upper power being worth it.

I realise that the K27/8 is the compromise that gives greater lag, however as I said the car is already 26/8 and I find it's characteristics acceptable (particularly after a T04e on a 2litre Cosworth), particularly with more overall power potential compared to low down drivability.

What is the power / PSI potential of the K27/8 ? does anyone have plots to show ?

Most importantly, Danno, can you provide a suitable starting (or preferably completed) map for this to go with the MAP 2 kit ?

Does the new J-pipe mate directly to the K27 without too many step changes ?

Still no comments on rev-limits with the greater air flow available ?

Would a different cam, such as the LR one, make a lot of difference at this stage ?

Likewise an enlarged throttle body, although I suspect not because of the limitation of the standard intercooler pipe size ?

Phil, I'm in Highgate and all the work is done in my garage or on borrowed ramps etc. Are you on titanic (www.titanic.co.uk/944) ?

Rick

Pheedbak

Hey rick ,

yer i was on titanic a year or so ago but now the volume of emails would scare my hotmail and i cant access that from work and delete stuff . I think ill set it up with my pipex which has a better tolerance for loadsa mails. Hmm well i used to have a 944 NA and was happy working on that cos it had engine bay space but theres just so little space in the 951 !! where do u start i dont even have much of a clue where the turbo is !!!

Anyhow for now the cars got some europroducts chips , boost enhancer , and a 3 inch s/steel exhaust made by hayward and scott .. which is luuurvely

Ive got a few issues with the car mainly oil consumption , and a strange noise (a drone if u like) i suspect the turbo hence i thought id see how u were proposing to get your new turbo togther , u just gonna buy the bits and plug it all together ?

Cheers

Phil

eastendr

The Hayward & Scott system is good. The boost enhancer is a very popular fitment over here for 951's, although I think the Reliaboost may overtake it.

Danno supplies it as part of his (Guru Racing) upgrades, along with wastegate shims.

If you look on my site, you'll see the full history of my ongoing 944 turbo developments. Look on the upgrades and options page for the whole story ...

http://www.cannell.co.uk

Rick

Pheedbak

Its all good , i enjoyed the site

Ive really got to sort my strange noise which thanks to an oil top up comes about less frequetnly now... i may try and get the stock turbo rebulit to higher specs i believe you can get garret bits in it to make it spool up etc . Then i wont have to tell mr insurance man

anyhow im sure ill speak to u on titanic

Phil

Bill_396

eastendr, the MAP II J-pipe mated to my k27/6 just fine. The only mod required is to the existing water line because of the larger turbo compressor housing, the Guru stuff fit right in for me. As far as your #6 or #8 question goes, my impression is that it depends on your intended use. For a stockish street car doing short blasts I believe the #6 is the way to go. For extended higher speeds, open tracks or when further mods are planned probably the #8 should be used. I'm happy with my #6 but in reality never exceed 100 mph (third gear red line) in my travels. bill

TonyG

To compare what a K27/6 & a K27/8 will do on a dyno against each other, you don't have to look far.

Since, on the above comparision, both turbos use the exact same compressor, the only difference being the turbines, and since these turbines come on the regular flavor 951 and the turbo S 951 respectively, just do a comparision between the said two cars.

What you will see is that the 6 hot side will come on at least 500-600 rpms sooner in any apples to apples comparision.

And while the 8 hot side has less back pressure (relative term here), and will allow the engine to pull stroner up past 5800 rpms or so... it really doesn't make much sense to use the 8 hot side simply because the stock 951 engine really won't make much power past 6000 rpms (at least not without a lot of other modifications). If you start doing apples to apples comparision, you see that the HP rolls clost to 6000 rpms in every case.

That said, it's obvious that the area under the curve with the 6 hot side is much greater % wise than with the 8 hot side.

A bigger area under the curve means more fun on a street car (and a faster street car).

On a track, it's a different story (if it's a high speed track).

Next is plain old lag. Drive a turbo S. It's got a ton of lag. Why? It's the hot side. It's too big. Now keep that same hot side, and had a larger compressor wheel (larger = more weight = more force needed to accelerate), and you get even more lag.


Here's a dyno comparision of 3 cars. Mine with a K27/6, and two cars with stock K26/8 turbos (all running stock air flow meters, chipped, hitting 16-17 psi boost).






From the dynos, you can clearly understand the area-under-the-curve thing. Also, from the dynos, you can see the HP improvement at compable boost/modification levels (all cars very close to stock).


Unfortunatley, I can't find my K27/6 vs K27/8 dyno comparisions... I'll keep looking.

But what I've found is that the 8 hot side isn't worth 30Hp. Not in my apples to apples comparisions. It was worth around 10Hp to the wheels.

I've also got somewhere, dyno runs of about 348RWHP at 20psi boost, with my K27/6 with the peak HP in at about 6000 rpms. I've never ever seen a K27/8 car make 30 additional HP (which would put it 378RWHP)!!!! At least not with 2.5 liter engine.

If you have a dyno with a K27/8 putting out 375+HP to the wheels (on a 2.5 liter car), SAE corrected on a DynoJet, I'd love to see it.

Also, my car that was running the K27/6 had the following modifications when it made the 348RWHP:


HR 52lbs injectors
HR adjustable fuel pressure regulator
HR ARC2 fuel controller
K27/6 turbo from Powerhaus
Bursh test pipe.
Borla XR-1 2.5" rear muffler
HR Stage 4 MAF Kit with HR hard pipes
Powerhaus head (stock valve sizes, stock cam, stock lifters, stock springs, stock retainers, stock everything, except that it was surfaced bring up the compression slightly, and had intake porting which could be described as minimal at best..... but it was running through a stock intake manifold and a stock throttle body, and a stock intercooler).

jimbo1111

Great post Tony. Very informative.
How do the Garrett's compare to the k27 turbine using a #8 hotside. Do they spoolup any quicker?

'86 944 turbo

I also want to know this since i'm soon getting a garret

TonyG

jimbo1111 & '86 944 turbo

That's impossible to answer based on the way you worded your question. Why? Simple. Because KKK (and the Turbonetics KKK replicas) only has 2 different turbine side "setups", whereas with a Garrett there are a ton of combinations.

To answer your question (if I am even able to answer the question..), I would have to know the turbine housing model, the a/r ratio, and the specific wheel being used, and then I would have to know the compressor wheel, housing, etc....

Also, if you are getting a Garrett, are you getting a real true Garrett? Which requires a modified cross over pipe, and a modified motor mount? Or are you getting a hybrid that uses a Turbonetics KKK replica hot side? Big differrence.


And at best... it would only be an educated guess unless you happen to be using one of the Garrett combos I've used which is unlikely.