PMO fuel injection questions:

[Nige]

.
From memory you've had this same dilemma at this time of the year for at least the past 5 years !!
.

At least 10 years I'd say

[911hillclimber]

Probably so!

Unless you have a good pot of money and can justify the spend and what you might gain it is hard.

Injection will make a nicer engine and cost 3 to4K and might give 10 bhp on the 260 of today's engine. That's not going to shatter much on a hillclimb.
My fellow competitors are all north of 500 in 700 Kg.

For double that I could have a sceammer of an engine, 8K rpm and the 50 bhp that will come with it still on simple carbs, electronic ignition.

I would have to sell my fresh 1972 Honda CB 175 to do that, and that makes it harder.

As to Andy's comments, very true. Competition cars are hard, you just want/need more and more to offset age, 70 next year.

The gear change hampered me last weekend at Shelsley albeit in practice. One gear change mistake cost me 2 seconds, simply changing from 3r to 2nd which ended up in 4th right in the start of the bottom esse.
I've been told of mixed results with the WEVO 915 internal gate, but have driven hard a 911/915 so fitted with the added WEVO gear shite tower and the change rivalled my Subaru Impresza which was really magic, good as an Escort Mk1 box.

A free revving engine would avoid on gearchange, maybe 2 on the hill, £8K is a high price for that.

The 3.2 is a bit fragile, the rod bolts are 8mm, the cams drop off steeply over 6500 so there is nothing more to be had from the current engine. Rotor arm is a 2.4/T with limiter so about 6400 tops.

As to also 'tinkering'; yes, and a full engine re-build sounds good for the winter!

If only it went as fast as this looks...

[Kirklands 904]

Graham,

I have a Clewett system on the 904FF (2.4S) and up to the time of speaking it has been absolutely bulletproof. I recommend it!

[911hillclimber]

Thanks Bill.
Can you detail what of thier's you have and what it does?
They seem to be hand-in-glove- with the PMO injection.

[Kirklands 904]

It has a toothed wheel on the crank and fires three coils in succession. Each coil fires a cylinder on each bank simultaneously I.e a dead spark. I'll look for the invoice and give you the actual part number. My engine has Webers.

[911hillclimber]

Thank you Bill, could have sworn you were on mech injection!

[andytat]

Hi Graham.
I have installed both PMO throttle bodies as well as Jenvey with various different cams
to 3.2 Carrera engines, both standard and enlarged to 3.4l using either Mahle 3.4l
cylinder and piston kits or JE pistons in machined and re-nicasilled cylinders. Mostly
looking for the best compromise between drivability and performance. 964 are great
cams and liven the lazy characteristics of the 3.2 engine very nicely. One thing regarding
cams is that I would never use re profiled cams as usually the base circle of the cam
has to be reduced to get the desired overlap which changes the relationship between
the rocker arm and the camshaft which can cause problems. I'm building a 3.4 engine
at the moment and have fitted a pair of 3.2 spec cams from Kent who were great to
deal with. They don't list them on their website so you would need to phone them and
don't forget to tell them to remove the power steering pump drive lug.
I have some info regarding throttle bodies that I'm not able to share on an open forum
but it could involve something very interesting for you, are you going to Boxengasse
tomorrow? I'll be there in my Speedster which is running Jenveys and DTA engine
management if you would like to have a chat.

Regards

Andy

[Kirklands 904]

Graham, I have found the invoice but it has no specific part number. It is described as a "911 kit with 116mm pulley , 2.4 litre and later" The current Clewett web site gives its price as $1279 which is what I paid three years ago!

[911hillclimber]

Bill; thank you again, I'll look at their web site.
Andy:
I was going but the wife was not keen, so going to a meeting at Shelsley Walsh tomorrow.
Your info is really good though.
I have had other advice from 911 owners with 'hot' engines and it is all making sense even.

The spec/actions is brewing:
Special aftermarket rods to take 8K red line. Not sure what make yet
ARP hardware for the rod ends.
Special pistons with valve pockets cut and forged/light. Same make as Peter K's engine
New ground cams on new blanks. Potential source found.
Rockers with mech adjustment to suit (strength and lighter)

With all that spinning the induction could still be the PMO's I have and analogue ignition, upgradeable later.

Transmission: WEVO internal shift kit.

Sewn the seed with the Boss, will cost me my Honda CB175 I think, but that's a kitty of £4000.

[andytat]

Sounds like a good plan Graham.
I think you have pretty good induction as it is, if a little more complicated to fine tune
than EFI. Making it rev is the key, and keeping it together at those revs is critical
and that is mainly the con rods job. Arrow or Carrillo would be my choice. Are you
sticking with 3.2l capacity, or going 3.4? The larger the capacity the more radical
you can get with the cams without loosing bottom end torque.
Best of luck with the project.

Regards

Andy

[Gary71]

Definitely do programmable ignition with all that.
You can push the advance so much harder than the stock curve allows on decent fuel.

[rhd racer]

Graham - in this month’s Porsche Post the Modified Register report has a 3.2 with a modified exhaust and 964 cams achieving 261bhp, which is a good starting reference. Read it today and thought if you!

Cheers
Wayne

[911hillclimber]

The engine today gives 260 bhp and a red line of 6500.
The engine was DIY rebuilt 5 years ago after a Big Blow-up at around 9K rpm...
All new inside, but solid at the moment after a lot of abuse.

Would stick with 3.2 as the barrels are v good so simple piston swop.
3.4 might make twin plugs a near must with high lift wedge crown pistons. Can't justify the cost.

I'll find that article Wayne, thank you.

I like Bill's Clewitt system combined with the near DIY carb tuning, £1300 is a big ask though.

My main goal is the rev limit so I can afford not to change gear with the clumsy 915 box despite a full re-build by MB Eng. That £1300 could benefit me more getting the WEVO internal gate fitted.

Frankly, it is hard to justify a lot of cost for quite small gains against class mates with north of 550 bhp and 4x4.
To beat them you need to join them and I'm on the end of my hillclimbing life after 30 years 'competing'.

That's not a heart sob, just simple reality.

[rhd racer]

+ Wayne Schofield remap!

[rhd racer]

Sorry, responses crossed over.

I think a 6500 red line seems pretty conservative. I would have thought comp valve springs alone would give you comfort to go further (accepting no power gain, just the advantage of going further in the gear you are in). It is fairly common practice to go 1k or so above the standard cut off without mods for a hill climb car