thingo

Yea I have a hta, it's a great turbo, though my 3L is a bit different to this one, I just have a mildly ported 951 head honed intake with a twin scroll housing/ crossover. Mine drops off past 5500 pretty significantly, though mine comes on about 500rpm sooner. The turbo comes on great and gives great power.

blitz951

That twin scroll must be great. My head is very modified. Nothing in that head is porsche. I felt the biggest weak point is in the head and the heads done in the porsche circles for the 951 were all coming up with the same end point so used someone that understood headwork from another perspective. My guy does v8's, air cooled vw, and hondas many of them drag cars. All the parts are important but the head is the limiting factor for the 951 in my opinion.

67King

FWIW, that head was the benchmark in the industry for a good 1.5 decades for out-of-the-box flow. It had the best flow coefficients of any production head darn near forever. Of course, the reason it flows so well is because of the shape of the head, with the port exiting on almost the "top" of the head, the short turn can have a very large radius. But it was really only with the maturation of CFD in port design that better discharge coefficients became possible.

thingo

Yes I am looking at doing something about the head on my motor, I know I am leaving a lot on the table, I'd like to find a 2.7 to use as a starting point.

Chris White

It took me a second to remember that 'Blitz' is the car owner, I know him by his 'real 'name!

anyway - to clear up a detail - the turbo is the Tial version of the GTX35. Tial made their own billet compressor wheel and the precision cast stainless hot side housing. Blitz and I went back and forth quite a bit on turbo selection, when this was being built the GTX35's were impossible to get. I had to pull some strings to get the Tial turbo. We looked at other turbos such as the hta but in the end we used the Tial version.

The cam timing has not been advanced - it is a JME cam so John has worked some of his own timing changes there. The only difference between the 12 and 20 psi runs is that I added a little more fuel to the 20psi run for a little more safety margin as well as a small amount of intake charge cooling from the vaporization of the excess fuel. You can see the AFR differences in the charts. In addition to the extra fuel the ignition timing varies according to boost, so there is less timing in the 20psi run.

The head porting is interesting. I have to admit I was a little skeptical at first (Blitz had the head ported by a west coast shop), it has the style of a V8 D porting job. I was expecting a little more difficulty at low rpms due do the porting but other than idle fluctuations is runs well at low RPM.

This car did see a lot of dyno development and tuning before this set of tests was performed. In fact the engine exceed the design goals enough that we had to change the clutch / pressure plate due to slippage (the failure of the torque tube bearings had some impact on that as well!).

BTW - the stock 951 head still outflows almost all the aftermarket V8 heads (under .500 lift). It is a very good design for a stock part, it does exactly what it was designed to do - midrange power.

Chris White

Thom - do you have a link to any of your dyno graphs? I am interested to see how much of a wall your are feeling.
An odd result of a flat torque curve is that it does not feel as exciting as a peaky curve. A peaky curve (like most highly tweaked NA motors) feels like it is building more power each shift while a flat curve feels like an electric motor, it just pulls all the time but it is not a 'explosive' as a peaky motor.

Thom

No dyno graph yet, because I was never really interested in knowing the output until the engine felt the way I wanted. Will be fitting a big cam very soon then dyno time sometimes before Winter. Unless the cam messes up the current balance but I doubt it.
With the stock intake engine acceleration would slow down progressively from 5500k-on. I could push it past 6k but it was pointless. That was most noticeable in 4th and 5th gear.
The engine isn't peaky at all btw, the shape of the current curves would certainly be like Blitz's with torque hitting earlier at 4k, probably thanks to the smaller turbo, and it keeps making torque past 6k.

Is that turbo a HTA or a GTX finally?

333pg333

Here's some graphs showing my old stock 2.5L motor with larger cam / GT3076 .82 and the current 3.1L which is pretty highly modified. Same fuel, boost, dyno, operator and I think weather was pretty similar too.

The tuners found that adding more spark up top didn't really change things much. Only brought knock a little closer. Interestingly they reduced timing lower in the rev range due to some rattle and the hp/tq picked up as a result. He remarked that he'd never seen anything like this before. The apparent 6k wall may be down to more than just the intake of course. Need to test b/pressure in other areas as well. Turbo is large (sorry Harry :-) )so I doubt it is the reason.

blitz951

Patrick what turbo/cam are you using?
Thom, its a gt3582r hta, by tial.

333pg333

Cam is similar to the 2nd from top on JME list. Turbo is a hybrid BW. Specs listed in my build thread. At the track currently so don't have them to hand.

A.Wayne

Super Big graph for big power .......

333pg333

Yeah nah...

Chris White

The graph is that big because Pat was using it to search for the missing power in his old set up!

Dutch944

And he never found it, that's why he just build a new engine! ;-)