Turkis Blue ST Hot Rod

Ferry Man · Post by **Ferry Man** » Sat Aug 01, 2009 4:04 pm

OK, here's some plots of the power data from the rolling road sessions.

You're looking at revs per minute along the base scale and power output up the right hand side.
The colour clarity in these photos is not good but basically the bottom of the three lines (in blue) indicates output at the wheel and the red line above that is engine output.
The third line (at the top) in orange shows the torque in Nm.

This is the state of affairs as the car arrived at Bob Watson Engineering.
The maximum power is 234 bhp (at 6,950 rpm). Torque was 245 Nm.
Rather disconcertingly there's an very evident dip in the power in the mid range.

Ferry Man · Post by **Ferry Man** » Sat Aug 01, 2009 4:06 pm

Bob changed jets, fueling, ignition and much more and got the engine up to 241bhp on the next run.
However, there was more to do.
These graphs show the third and fourth run and I include them here only because they show a fascinating insight into the 'caps on' or 'caps off' conundrum.
The poor performance in the middle isn't yet resolved in these but don't worry about that, we'll just concern ourselves with the power ratings for now.

CAPS ON

CAPS OFF

So, with the caps on it now shows a stonking 253 bhp.

And.... with the caps off the power leaps to 254 bhp.

Yep 254. So that's a gain of 1. Or in laymans terms, one.

Now, I guess if you're riding a horse then one horse power is important but in this application it's laughable. I did laugh.
So, not even statistically significant. Mind you, I love my exhaust, it sounds fantastic. And it looks cool. I wouldn't be without it and I'm happy to have paid more for a modified one. But it don't make your car go faster.
Therefore (and this has been proved before) you can take it from me... "the standard Porsche designed exhaust is a very efficient bit of gear".

Ferry Man · Post by **Ferry Man** » Sat Aug 01, 2009 4:07 pm

Oh and... Go back to those graphs and look at the 'caps off'. Right at the end of the rev band (around 7,000 rpm) the power actually falls away sharply compared to the standard set up. Odd. Probably lack of back pressure. I shrugged.

Ferry Man · Post by **Ferry Man** » Sat Aug 01, 2009 4:09 pm

Anyway this is the important one. The fruit of Bob's endeavors.
You can now see a peak of 260bhp. Two-hundred and sixty. TWO-HUNDRED AND SIXTY.

That's maximum power at 6,750 rpm.
More importantly the power curve is linear and climbs evenly all the way up.
Also the torque is strong from about 3,000 rpm to the limit (the horizontal, nearly flat curve).
Maximun torque is now 274 Nm (at 5,750 rpm).

Thank you Bob, thank you Nick (Redtek) and thank you Nick (early911).
I think that is an excellent result from that engine. I'd say it's well built and finely tuned.

Highfield · Post by **Highfield** » Sat Aug 01, 2009 5:40 pm

Ferry Man wrote:
Highfield wrote:just mind the driver doesn't take it over the 1,000KG
Ooh, that hurt Ian. I nearly missed that comment, can you give me any dieting tips?

Sadly not Paul.

This is what it took to replicate me in the seat when at Center Gravity for a demonstration of how they do corner weighting, substituting weights for the driver.

Ian

Highfield · Post by **Highfield** » Sat Aug 01, 2009 6:06 pm

Paul

Hope you don't mind but I thought I would post up the 256bhp graph from my 3.2 Carrera Engine I had. Peaked at 240 ft/lbs torgue.

So on paper, fairly similar, but in fact very different in construction and feel etc. I am sure.

Your peak power is produced further up the range and revs much higher in total and must spin up a lot quicker to those revs.

However, I am not able to afford such a lovely powerplant, so keep coming back to 'what if I did a 3.2 transplant'.

I know the 3.2 is a slower engine to rev, but it was very torquey and a pleasure to drive - I just wonder how it would feel in the early and lighter car.

Also, if you remove the injection from the 3.2 and replace with carbs (love the look of carbs), do you loose a lot of that torque and power ?

Anyway, enough hijacking, and back to looking at your build again as it is such a wonderful car.

Ian

Ferry Man · Post by **Ferry Man** » Sun Aug 02, 2009 11:47 am

Highfield wrote: Your peak power is produced further up the range and revs much higher in total and must spin up a lot quicker to those revs.

The engine is wonderful. It does spool up so quickly. The revs rise so willingly to the limit, it's intoxicating.
On twisting roads, when you're working through the gears, the rev counter needle dances frantically from left to right (all the way to the right

).
I've never known an engine so easy to rev.

964RS · Post by **964RS** » Sun Aug 02, 2009 1:43 pm

Surely thats no where near enough weights on that seat?

210bhp · Post by **210bhp** » Sun Aug 02, 2009 2:54 pm

Thats a great result Paul. Nice to see that the build has come to it's full potential. I can tell you are mighty pleased. Nice when things come out as planned isn't it?

Regards
Mike

Gary71 · Post by **Gary71** » Sun Aug 02, 2009 4:25 pm

Superb result

What did Bob change to fill in the big hole in the curve?

Highfield · Post by **Highfield** » Sun Aug 02, 2009 4:27 pm

Paul

I can imagine that rev counter on your car

What makes your 260bhp rev so much quicker than a 3.2 with 260bhp ?

Is it down to a short stroke and big bore ? Or the heads and cams ? Or the induction ? Or etc. etc.

Ian

Ferry Man · Post by **Ferry Man** » Sun Aug 02, 2009 4:59 pm

Gary71 wrote:What did Bob change to fill in the big hole in the curve?

Lots of changes all added up but the biggest improvement to eliminate the 'hole' was the emulsion tubes.
As I understand it the emulsion tubes vary the diameter and location of small holes within it. My carbs now run F2 tubes but the numbering sequence doesn't seem to mean much to anyone except maybe Bob. Some tubes richen the mixture up at the bottom of the RPM range and under acceleration whereas a different selection could lean the mixture out on the top end.
Apparently there's 18 different tubes to pick from. And then you need to re-jet again to suit the relevant tube. I think.

911hillclimber · Post by **911hillclimber** » Mon Aug 03, 2009 5:53 pm

I saw this car on the rollers at Bob's while picking up my Lola racer.
I'm sure envious of 260 bhp...
You must have stolen some from my miserable 200 bhp 3.2 on webers, and please can I have them back!

Such a nice car. I saw it with the big dip in the graphs, and Bob said the F2's should fix it.

What spec headers do you have on the 2.8 please?

Rickard M · Post by **Rickard M** » Tue Aug 04, 2009 10:26 am

nick-moss wrote:
But what will it do to the venturi airflow into the stacks?
It's something we can test on the rolling road

Did you try with the tea strainers from page 37? And the Redline thing with two hexangonal meshes, sandwiching a thin foam filter.

Lovely car by the way!!

Ferry Man · Post by **Ferry Man** » Tue Aug 04, 2009 11:09 am

Rickard M wrote:Did you try with the tea strainers?

Rickard,

No, we didn’t try the various filtration options on the rolling road.
I’ve decided to run with the standard PMO filters & weather shields.

My reasoning is that though engine looks fantastic with the tea balls, I have a hesitancy to run like that at all times because of worries about dust ingress. I’m concerned for my engine’s well being and, in all honesty, I’ve got a lot of money invested there. ‘Be a shame to risk that.

I drove the car a few miles to a photo shoot with the tea balls and it felt/performed slightly differently. Not much but enough to feel it would benefit from different settings. So, faced with the idea that switching to different filters meant altering Bob’s good work, I’ve resolved to leave alone. I’ll consider the mesh filters for ‘show’ only.