924Board.org

[indi9xx]

Just thought I would post an update on the new improved modified performance cylinder head we have been working on.

The first project car has been back in the hands of its owner for over a week now with no issues.

Just before the car was returned, it was briefly dyno tested with a couple of power runs, which netted about 139BHP peak (6500rpm) from a standard high mileage 924 with less than perfect compression and leakdown readings. I say peak, but the horsepower and torque levels were anything but peaky.. just a clean power curve (torque and BHP) from idle through to 6500 rpm, with improvements across the board and no loss of power at any point on the curve.

Here is what the customer (Julian, a Tipec member) had to say in an email today.

"it's very impressive. I wasn't too sure what to expect,
but this is quite a bit more than I was hoping for. Not only does it have
more punch, but it has significantly more power across the full rev range,
and the torque appears to have been increased too. The sounds amazing too,
especially the induction roar!"

What he mentions about the "induction roar" is very interesting and something we instantly picked up on. Due to the improvements in the intake port, as the RPM increase, the engine produces a distinctive induction sound. This is an artefact of the improved head causing an improvement of the pulse length tuning characteristics of the standard manifold and plenham chamber. The negative pressure waves are entering the plenham of an increased amplitude, which as well as creating an excellent induction sound, are also assisting in drawing in more air as the rpm increases. This was something we had hoped for during the design and development, but none the less it was very pleasing to realise it had actually worked.

It would seem that Porsche did a very good job of designing the intake manifold and even the stock injection system, which adds more weight to the argument that Porsche designed the standard cylinder head to choke the performance of the engine and hamper future efforts at improving the performance of the 924 (So the cheap Porsche would not keep up with a 911 on a track which just would not be cricket!).

We were concerned about this particular 924 having a less than perfect bottom end (slightly low compression readings), also Julian was in a rush for his car back as the project had run on a little, so we didn't spend as much time on the dyno as we had hoped. However Trevor Wilson, a previous member of this forum, will be having one of these heads, fitted to his car in the next two weeks. So we do plan on getting some readings from his car, both before and after fitting the cylinder head, along with compression, leakdown and other details before and after the head is installed.

Eventually, we plan on rebuilding a stock 924 engine, dynoing the car as soon as the engine is run in, then changing the head to one of these items and dynoing the car again, so there is clear scientific data to back up our claims. This car would probably end up being a demonstrator for our 924 performance products and workshop loan car.

We are also working on our "Mother of all 924" projects, which will feature one of these heads, our own camshaft grind, jenvy throttle bodies, omex engine management, an improved bottom end and distributorless ignition for a customer with more money than sense! Currently the project is running at about £11,000!!!!!!!!! (including body kit and everything else!)

Anyway, just an update for those who have expressed interest.

Jon Mitchell
Independent Porsche Specialists
Bournemouth, UK
jon@9xx.co.uk
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Jon Mitchell
Independent Porsche Specialist
Bournemouth, UK

[wdb]

was everything else stock .. cam timming afr , etc. ?

[Lizard]

Good to hear Jon, I am very interested in hearing the outcome of this, when do your advanced heads go up for sale for int orders? and what is the price we will be looking at in USD and CDN pls.
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3 928s,

[indi9xx]

This first test car was running everything 100% stock except for two items which on a stock car have proven to produce zero results on their own. These two items were a Audi throttle body and the removal of the snorkel on the stock air box. Normally these two modifications have absolutely no bearing on performance when tested on a rolling road (although some claim that their car "feels" faster)

We also tried the car with the standard throttle body and the snorkel fitted (although on the dyno), while the performance was down a fraction (it was hard to tell) compared with with these two items, it was only a slight loss (but still a gain on the stock head) if a loss at all at very high rpm.

The air fuel ratio was still governed by the standard injection system, with the fuel mixture set to 2.5% CO at idle and the ignition timing set to 8 degrees (typical euro specs). The cam was timed with the standard 924 cam pulley, to the standard marks.

Price is still to be decided on, but it will be either bellow or equal to £500 sterling, but if lots of people wanted them, costs to build these heads would go down and so would the price. Shipping to the USA would be the biggest headache and could be expensive. It would work out cheaper if several US/Canada 924 owners clubbed together and had several heads sent as a consignment to one location for re-distribution.

There is just a little more development to be worked on with this head, namely seeing how it responds to camshafts, larger valves and further refinement. But that will be happening over the comming weeks.

Once we are happy with the head as a product, we would be able to market it... the main mission however has not been the development of a product, but to solve the 28 year old mysteries of the problems in tuning the 924 2.0, if we manage to sell some of these heads, then all the better, but you would be paying for the work performend, we dont expect to earn the development costs back.

Once our work on this head is complete, we want to move onto developing a right hand drive 924 2.0 tubular 4-2-1 and 4 into 1 exhaust manifold (I think there are already LHD items available), a cost effective 924 2.0 twin carb manifold (unlike the webber item which is a little expensive) and some parts to improve the performance with the 924 2.0 turbo (including an improved breather system, intercooler, boost/detonation management computer and more)
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Jon Mitchell
Independent Porsche Specialist
Bournemouth, UK

[indi9xx]

One thing I forgot to mention, we are working on alternative ways of modifying the intake port in a more cost effective way. One such way is the use of ceramics in the intake port, rather than the current metal filling and machining methods.

The other problem with selling to the USA, would be the fact that in the UK we will be providing the heads on an exchane basis (seeing as otherwise the supply of heads to modify would dry up here) but sending used heads from the USA to the UK for exchange would increase the cost even further. But this is just a bug to iron out!
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Jon Mitchell
Independent Porsche Specialist
Bournemouth, UK

[924guy]

wow,sounds like a huge step in the right direction!! im curious how this will affect performance at high speed.. the stock n/a seems to have a tendancy to get a little thready towards the top of the scale .. id bet there will be allot of very excited racers if theres a signifigant improvemnt there as well...
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Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

[indi9xx]

The top end performance is much improved. In fact throughout the rev range the performance is much improved.
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Jon Mitchell
Independent Porsche Specialist
Bournemouth, UK

[924RACR]

Wow, very cool...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Chrenan]

This sounds like an amazing development, very exciting. You could probably make a few sales if you partnered with an independent shop on this side of the ocean that could perform the work to your specs. Of course, that comes with a whole bunch of issues around intellectual property and the costs of development.
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1987 951 - M193 Version for Japan

[indi9xx]

I am currently dreaming up options for getting the heads over to the USA.

It seems as if its almost as cheap to send 5 or 10 heads to the USA as it would be to send just a couple individually.

Choices at the moment would be..

1. Group purchases. If 5 people were to get together, buy 5 heads, have them shipped to one destination and arange distribution from there.

2. Find a company is the USA which I can trust to keep a stock of 5 to 10 heads, to distribute the heads from a central location.

There must be a better way.. I will continue investigating options.

Today I have also been in talks with a camshaft manufacturer for the production of camshafts to specificly work with this head exploiting its improve flow and port velocity. As the camshafts currently on the market work on the basis of a "fix" for the poor head design which stop conventional performance cam profiles from working well.

Interestingly, as a side note, the standard 924 intake port would actually make a great exhaust port with use with radical cam profiles where avoiding back flow becomes important, this is due to the standard ports poor ability to flow from the manifold to the valve.. which also makes it such a poor intake port!!!

I would also like to point out that this head is not a simple port and polish job. The route and shape of the intake port has been completly changed, which has actually seen the port volume decrease. The latest version of the head actually see's port velocities increase through the roof, while flow rates are also up. Whereas every other head for the 924 with a port and polish always see the port volume increase and port velocities decrease. Some do not even see an increase in flow!

I also need to point out that the head developments so far have been for normal, non turbo heads.. the turbo head in now way anything like the NA head and our current research does not apply to the turbo head.
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Jon Mitchell
Independent Porsche Specialist
Bournemouth, UK

[Vince Ponz]

Remember they have 125hp cars. We have 95 or 110 depending on the year. Still 11HP is not bad.
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"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

[Joes924Racer]

Hey I posted on your yahoo group from across the pond...
I need to dyno my car. Good luck
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

[Robert Hooper]

Porting of head sounds interesting, but i have had the head on my race car ported and everything is standard as per your example and i have netted 138 Hp as well. (i run in a production class champoinship) If a standard p-p can net 138 hp what is majorly differnt about your porting job that would make us want top purchase your head ?
Do you have any photogrpahs to show us what you have done, or dyno printouts?

I understand that your company has put in considerable time and money im just trying to understand what you are offering differant to any other porting job which could yield the same results. If people purchase a head from england then they are going to incur large shipping costs, they could just spend the money porting the head at the local performace shop....

Cheers

Rob
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1982 924 Race Car
1981 931 Road Car

[endwrench]

In conjunction with Robert Hooper's question, how did you both arive at your HP figures? I know Indi9xx used some style of chassis dyno and evidently did a conversion to flywheel HP. I am always a little suspicious of chassis dyno figures because they vary so much from dyno to dyno and operator to operator. Of coarse the same can be said of engine dynos but at a much lesser degree. Also, I have never seen a conversion to flywheel HP that was anything but an educated shot in the dark. Some sort of back to back before and after testing would be the most telling. Please do not take this as any kind of snub at your efforts. I think what you are doing is excellent and the information you are sharing is very generous. I think other testing could actually make you efforts look even better!

Todd

[iwantacarrera]

Hi Jon,

Glad to see things are progressing well. I have been reading about this head for a while now and I am glad to see you righting the terrible wrong that Porsche committed by restricting the head in the name of one-downmanship.

Anyway, I will be keeping check on this. I think your approach of building a stock engine for a back to back OEM/Mitchell swap test is the acid test. If all is good (i.e. if the head works as well as hoped) then it would be a great boon to us NA 924 owners.

I think that given that the head is also limited by the ancillary equipment (inlet manifold, exhaust, fueling etc) later testing with your upgraded cam et al will yield even further gains. It will be interesting to compare figures from say a 924 with Piper cam, exhaust and induction kit to your car with similar modifications.

As for the price. £500 isn't the earth but if enough people bought it then the possibility of a £300-400 head would be nice. I for one will buy one subject to further details.

Keep up the good work. See you on the TIPEC tech forum

Paul
Another UK 924 owner!
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1981 Porsche 924/80 Porsche 931 GT rep