Special getting closer...

[KS]

OK, just a suggestion. On the dyno/rolling road, the engine makes good horsepower, yes? On the hill, it doesn't appear to, therefore it must be something that happens when the car is in action.

Have you considered the air flow over the engine/carbs on the move? Is there a vacuum (or at least, a low-pressure area) being formed over the engine, caused by airflow being deflected by windscreen, driver, roll bar etc?

Airboxes which allow the carbs to draw in still air might help, rather than leaving to their own devices out in turbulent (or non-existent) air flow. This has been proved to work on large-capacity, high-rpm drag cars, so maybe the case here. As I say, just a thought...

[911hillclimber]

Two things here:

1
Thanks for the lateral thinking! Will ponder this thought.
2
New issue of Classics is out!

Thanks Keith.

[Northy]

Could you ditch the carbs and put EFI on it? Or are you restricted in the class you run? You'd get good money for the carbs, that might cover some of the costs of putting Throttle Bodies on it. Carbs are last century tech. Mappable through the rev range, Fuel injection has got to deliver better results, surely?

Put EFI on it and take it to Wayne Schofield - he will get the best out of it.

Just means you're taking quite a few steps back to make a leap forward.

Don't loose the faith though, it's a cracking looking car and will be worth the effort, I'm sure! I love reading your updates, so keep them coming.

[gridgway]

there's no need for EFI surely? It's just a case of solving the problem with the current setup!
Graham

[911hillclimber]

Injection has been well looked into.
Jenvey do a set-up for the aircooled 911.

However it adds a bit to the cost and to the complexity to mod the car, but this should all work. It has given 269 bhp!

As to Keith's ideas of air flow, there is the actual engine in it's last body in posts on Porsche pictures in the general section.
Wide open but less carb filters.

I hope the silencers will bring some zipp into the engine this weekend.

Bob's rollers are accurate as we all know, so why does it not feel fast?

A pic to remind me how good hillclimbing is in the car!
Keith, you can see how the carbs are well in the air.

[gridgway]

Bob's rollers are accurate as we all know, so why does it not feel fast?

And that is the $64k question! I have no idea really, but the car is not set up properly despite the headline figures on Bob's RR. My 2.7 RS Rep did a 230bhp at Bobs and still ran like a dog. That was a timing problem, the dizzy was knacked. No idea what the actual bhp was when that was fixed, but it went from a limp shite thing to hooligan in the course of a dizzy change!

And I'd care to bet it's not the exhaust. Running on the new pipes will probably be better, but it hasn't solved the problem!

Armchair observers? Love 'em!

Graham

[KS]

As to Keith's ideas of air flow, there is the actual engine in it's last body in posts on Porsche pictures in the general section.
Wide open but less carb filters.

Keith, you can see how the carbs are well in the air.

OK, first of all, you say there's a picture of the engine in its last body LESS filters. Can you make a run without the filters?

Also, It's not a matter of the carbs being simply out in the air. I've not seen many cars (I say 'many' but in fact I guess I mean 'any') cars using these filters with the rain hats in this sort of configuration. I'm used to seeing that style of filter in a car with an enclosed (ie, still air) engine bay – 911 etc. I think the flow of air past the filter hats is actually pulling air out from the filter/carburettor and starving the motor of air at wide-open throttle.

If it was me, I'd make one run less filters to see what happens, and then fabricate a 'still air' airbox for the carbs so that they draw non-turbulent air.

This is the set-up on a friend's VW in the USA – the carb inlets are inside a still-air box sealed off from the engine bay and enclosed by the rear spoiler and bodywork (removed in this photo). The carbs can only draw still air. The engine produces just shy of 300bhp from its 2.3-litre capacity, so can definitely breathe just fine. Like I say, just a thought...

[steve wright]

I think Keith is onto something, not that I have anywhere near the experience of many of the people on this Forum! But I've had the same experience with a dyno - it's not real world. Sounds like you need to start changing one component at a time in real world scenario's, for example as Keith suggests taking off the rain hats in case there is a vacuum issue, or changing the dizzy after one run up the hill. Is the coil new? Might be worthwhile changing that even if it's newish as they can rapidly deteriorate and give the symptom of loss of power under load... as do condensors (although I'm not sure if the 911 dizzy runs one like the VW).

I can understand the frustration now but it will all be worth it when it comes right though!

[911hillclimber]

To the filters:

At the last hillclimb we ran a few tests.

First was to remove the filter/hats and run open venturies. The car went 1 second faster than the run before.
Same track conditions and me a bit more confident.

The Lola ran a time just 0.6 sec slower than my 350 bhp 4x4 Impreza on slicks (very modified suspension).

Encouraged by this, I had very very special dispensation by yhe Officials to run the car without silencers (110 dB)

Left the start line in a blaze and grabbed 2nd only to bend the linkage/box selectors (prob the former as the box was stripped/checked and found to be straight) so i never got the chance to open it up.

At Shelsley this weekend (a very steep hill) I'l be running open carbs and the new silencers. I know this very narrow hill well so if dry I can compare.

To the dizzy:
Graham has told me this before, and willing to try anything i have borrowed from the VERY helpful Mike Bainbridge an SC dizzy with electronic ignition and matching coils.(USA origin).

The current system from Aldon Automotive is all new, every bit.
All the weights move well inside.

Could this be the dizzy not allowing the engine to get going from 3K upwards?

The 269 bhp RR run is on You Tube.

When the Lola was first built by them it had a Pinto 2 litre in it on a stock ford weber, but air was fed via an air box to one side of the drivers head, a bit F3 style.

Be a shame to hide those PMO's!

Terry Davison ran this engine in his Nomad sports racer, very similar to my car with the top open, no filters etc.

Can we be getting somewhere gents?

Thank you all for taking the time to help me, much appreciated.

The car sounds very different now, very low frequency sound than before.

[2.4TE]

Although I haven't commented before, I've followed this thread with interest. Keith's comment and the photo of your car reminded me of Bernoulli's principle- that which generates lift on an aeroplane wing. Could an explanation of your troubles be that the air rushing over the top of your car is generating negative pressure above the carbs, which are therefore essentially starved of air when the car is at speed?

[911hillclimber]

Thanks for the thinking, but let me say:

The car is 440 bhp/ton ish.
From a standing start it is 4500 rpm, dump the clutch and the LSD bites and so do the 14" wide AVON slicks. It pulls 1 g of acceleration.
Pull into 2nd at about 35 mph and it feels quite fast, but nothing special. so, I can't see the body starving the engine top at 40 ish mph.

3rd then is the same dull response, and 4th the same again.

However, on the rollers there is nothing like this, so i do not discard these good thoughts.

The engine did feel better without the carb filters on and the time showed it.
I've never had the gearshift problem before, ever, so maybe with the exhaust open it was breathing much better but 2nd simply slid away, no bangs or crunches, all very strange.

Some who have watched the car say the engine sounds like it gives in at 4000 ish +. This is not the case on the video on Bob's rollers. The car screams round the rev counter loaded up in 4th and to 269 bhp.

I hope Shelsley is dry so i can press-on up the hill.

[gridgway]

3rd then is the same dull response, and 4th the same again.

Is that the description of a throttle response problem? Did you test throttle response on Bob's rollers (if that's possible)?

[dragonfly]

Probably way off, but is the fuel supply sufficient under max load? I'd guess running up through the gears on the rollers isn't as aggressive as a launch up a hill.
Alternatively, could the fuel be sloshing away from the pickup under acceleration, which wouldn't be seen on the rollers either?[/img]

[911hillclimber]

Red top pump can deliver more than enough I'm told, and the pressure has been doubled since Bob's RR session!

All runs with 2 gallons minimum in the tank which is full of anti 'slosh' foam so that should be good too.

Good thinking though.

[IanMcLeod]

So I'm guessing after changing gear you go foot to the floor for wide open throttle. This is may be different to how the car is being driven on the rolling road to test HP.

Do PMOs have an accelerator pump in them to dump additional fuel down the throats when going rapidly to wide open throttle? Is the carb going lean in this condition?

Wide open throttle is also where the venturi the main jets come into play.

Ian.