Porsche964FP

I rest my case. Alright; fine. Bespoke engines require constant development - research and testing. His findings on PMOs are applicable - however every engine is different. No engine builder has ever stopped learning his trade.

NineMeister

Frank,
Should you wish to bring your car up to sunny Warrington, I'm more than willing to assist you and Nick test the PMO's and run more back to back tests on our dyno with the 9m ITB system, the TWM system, 993 Varioram or a 964/993 non-varioram intake. It will probably take us a couple of days to test everything, but at least then you will have a better idea of where to go next without buying more parts. Obviously I can retune the Motec for all the variantions we decide to try and should more time be available I also have a set of headers we can play with.

Let me know if I can help....

Porsche964FP

Hi Colin,

Thank you for the offer. As much as that all sounds amazing, it's a question of cost and I don't believe I can afford that level of development - testing.

EDIT: Colin, could I have some more info on you 9M ITB system?

kenloen

Can I ask .. Has anyone experience of the flat slide carb setup? I tried a set on my ZX7R few years ago, bike I know, but I4. anyway what a pain in the ar$e, having to feather the throttle most the time, ropey as f*** at low revs... Unless wipe open screaming playing large, I found them awful compared to the SU setup and swapped back (and I spent time testing)..

NineMeister

Frank,
In the past when we have built new variations of 9m engines we would expect to spend a couple of months or more testing combinations of intakes, tract length, cam timing, exhaust lengths and mapping. Cam timing aside, what I'm offering is the help to do the majority of that work inside a week. In terms of cost, spending less than 10% of your budget to have definitive answers sounds like a win-win situation to me.

Either way, no point in discussing this further here, so if you want my help or info on the 9m ITB just give me a call when you have a bit of time available.

Babalouie

It's possibly not comparing like with like, as your Kwaka would have been more highly strung with bigger cams and set up for a higher rev range. Relatively speaking, a 3.8 flat six with street cams, would give a much bigger suck through the flat slides at low revs. It might work.

ras62

Some interesting reading & advise here

http://classicinlines.com/TBI_QA.asp
http://classicinlines.com/CompressionR.asp

boxsey911

I haven't got the understanding or knowledge of intake systems to comment about the best way forward being discussed here. However, my concern about all this chatter is that moving away from the standard inlet system, is going to lead to a significant increase in induction noise. The result being that the car will end up being very quick but too noisy to get on any tracks over here.

NineMeister

Noise.
Most circuits only test static noise levels which are conducted at 0.5m from the tailpipe at an angle of 45 degrees. ITB's will not affect this measurement significantly with the engine lid closed.
Some circuits also measure drive-by level, usually at a point on the track where cars are running at full throttle. This measurement would be affected with ITB's which run with open tops or even when covered by a foam filter.
The solution to the drive-by noise issue is to completely cover the ITB with airboxes and relocate the air filter to feed the airboxes through a balance pipe. We've done a couple of prototype airboxes (low line with standard spoiler, high version for RSR spoiler) and one customer made his own system. The airboxes do not have significant affect on performance.

NineMeister

It's an easy one to work out Steve, this is the answer in a nutshell:

If you decide to use a 964 resonance flap intake manifold or 993/993RS varioram intake manifold the engine builder should tune your engine to make peak torque at 5000rpm and peak power no higher than 6500rpm. This should be good enough for 350-375hp, depending on the choice of pistons, cams & exhausts. However, if you want to make more power than that and build the engine to run above 7000rpm, to get the best from the engine you will need to run an ITB set up.

As far as I have deduced there are no exceptions to this rule, we have never managed to make significant power above 7000rpm with the stock Porsche intake systems. Even back-to-back tests with a 993RS & 993 varioram intake only proved that the RS varioram made less torque than standard. Maybe the limitation is the way we tested them or the cams we used, hence I would actually look forward to someone proving me wrong....

That said, here is the best example that I can give. The engine was a modified 3.6 litre 964RS engine running an early 9m ITB set up with large airboxes until the day when a new owner decided he wanted to run aircon - and the cheapest option was to fit a stock plastic RS resonance flap intake. The power curve shows rear wheel hp on our dyno, the shape of the curve is typical of our findings and proof of my take on the intake decision process.

911Jetta

Thanks Colin! I'm learning a lot here. I have big dreams...one day.

boxsey911

Hi Colin, this is what concerns me the most having experienced first hand how marshalls are inconsistent with their testing. We could easily see them picking up the extra induction noise on the static test and failing the car even though, as we both know, 911s are generally fine on a driveby (the main exception being 997 gen2 GT3s at Donington).

P.s. thanks for the insight into inlets, ITBs, etc

kos11-12

very interesting !!

Porsche964FP

Just want to say thanks to Colin for providing such insightful information in this thread - I feel It's become a thread that will be helpful to Rennlisters. Mission accomplished.

Also I've got a question, how many mm are 993 RS guides?

10% of my budget is an implausible amount for me. My engine build is currently on budget - through and through. Nick has pledged that regardless of over time, and whether we go with his slide ITBs or another brand he will charge me what was quoted. The development tests he makes are investments made by him not me.

Now, I'd love (and I'm sure others also) to have more info/ specs on your 9M ITB setup?

Brilliant solution!

Great - thanks Ras.

From my understanding. With all the specs so far an intake system as above wouldn't work on my car. Just superficially the RSR cams would be wrong.

So far we've specced the engine to rev in this range. So I don't see a point in testing intake manifold setups - 993 Varioram or a 964/993 non-varioram intake.

These are Nick's findings also

Hmmmmm.... I'll be researching that one! Thanks Steve - always the voice of reason.

Porsche964FP

Following your post on the Rothsport system - they have all the parts in stock and do resonance plenums for their ITB set ups... noise regs may no longer be an issue.

Watch this space the solution may be coming...