Special getting closer...

911hillclimber · Post by **911hillclimber** » Sat Jul 09, 2011 9:19 pm

What a day at the races today!
Loton Park Clubby meet, 3 in the class, clear blue sky and everything to go for.
Bloody hell Sean, you have done me a great chassis!
A TOTALLY different car to drive on this long tricky hill. All the hard parts have become silky, even the dreadded kink along Cedar Straight was flat in 3rd where last time it certainly was not.
The car turns, stops and switches direction as i always hoped it would. Amazing difference and an absolute delight. My smile was 720 degrees round.

The odd twitch and even a nice slide was caught by letting the wheel slip through loose hands, catching the opposite and planting the throttle, just sublime and FUN, at long last i've had a great day with the car.

I won my class.

The first practice run felt very good, even though the engine was 'off' and I missed two gears, the second run in practice was really good and resulted in a 2 second drop in times (massive change in hillclimb terms).

The first competative run was great, all worked correctly and i actually used the brakes, but there was a difference.

As an experiment to try to understand this problem engine we took the air filters off and this saved a 0.9 sec off the practice time. I think this was more to do with me getting more confident, but 0.9 off.
As a special 'favour' i was allowed by the officials to remove the silencers for the second run. That is a MAJOR concession and did the car sound gooooood!
A 911 flat six on open pipes made the paddock jump (110 DB), two times louder than the silenced car @ 108 DB.

However, most interestingly, the tick-over rose from 1000 rpm to 1600 rpm, so the huge silencers are infact restrictive.

The car now sounded like a full-on Targa Florio Porsche 906 (dream car) and to the line I went for my second run.

Blasted off in first off the start sounding like a banshi Porsche, grab second....and the gearbox went dead.
No second and i could get first/3rd/4th but not 2nd. Failed run and a crawl back to the paddock like a wounded racer..

I think a selector fork has slipped or bent.

However, that aside what a fab day. PB, fab handling chassis and some further insight to the engine. Wonderful and a real joy.

Have a 4 weekend break now from the season so will be quiet for a change. Just time to do the box!

YESSSSSSSSSSSSSSSSSSSSSSSSSSS

johnM · Post by **johnM** » Sat Jul 09, 2011 9:40 pm

Really pleased you have made some progress and found your smile. Hope you get your box sorted.
Kind regards

myatt1972 · Post by **myatt1972** » Sat Jul 09, 2011 9:50 pm

Fantastic news!
After following this thread avidly my smile is almost as wide as yours.
Well done.

58A - 71E · Post by **58A - 71E** » Sat Jul 09, 2011 9:51 pm

I've read this thread with interest for some time Graham; smiling for you

Bruce M · Post by **Bruce M** » Sun Jul 10, 2011 12:32 am

911hillclimber · Post by **911hillclimber** » Sun Jul 10, 2011 11:14 am

Nobody can smile as much as me!

Gearbox coming out now so the selectors can be sorted. The neutral of the 'H' pattern is at 45 degrees and not straight across and there is a dotchy feel to the gate across from 2 to 3rd, so something has shifted.

will return it to Mike at MB Eng for a sort-out.

On the engine side so much was noted:

- The car felt better with the filters off the carbs. The inside of the filers (the tin part) was wet with petrol/oil deposits both banks.
- When we removed the silencers and ran the engine the tick-over rose from 1000 to 1600 rpm.
- When i needed to quench the headers to allow me to undo the clamp bolts on the silencers using water, the one bank was VERYVERY hot, and the other considerably cooler, as in considerably.

Why would the engine run so hot one side to the other?

A 911 engine sounds bloody great open piped!

With silencers the noise was 108 DB, and without 110DB

Back to the garage.

MikeB · Post by **MikeB** » Sun Jul 10, 2011 1:18 pm

Graham

Great to hear you are a happier bunny

If you can repack the silencers, do that and check that the centre tube is still the proper shape.

I would imagine that the hot bank is running weaker fuel mix than the other bank. Could be lower float settings, restricted fuel flow ( if you have individual PMO filters) , or if the carb balance is out.

If you have the box out, why not take the engine to a dyno and see what's up?

911hillclimber · Post by **911hillclimber** » Sun Jul 10, 2011 2:19 pm

Box has just hit the floor!
Nothing in the oil or on the drain plug, and nothing loose inside with the side cover off!
Mike Bainbridge is in touch and he will fix it in a jiffy!!

Be nice in the south Lakes just now.

The carbs must be out somewhere just as you say. I have a full set of jets to PMO spec ready for Bob. When the box is back in the car will go back to see what is out.

The huge silencers can be 'seen through' so are wide open but obviously do restrict things.

Getting there now though. The car is now less than a second off my Impreza times at Loton.

The 911 on road tyres: 61 secs
Impreza on slicks : 57.69
Lola: iffy engine ; 58.16

911hillclimber · Post by **911hillclimber** » Wed Jul 13, 2011 6:46 am

300 mile round trip last evening to Mike at MB Engineering to have a looksee inside the box.

Found a bent selector fork....

Back together by friday and collected, pint of delectable Dent Beer in a hotel locally and back to the garage, in the car by sunday lunchtime!

Need to get some new (home-made?) silencers now and down to Bob's for a tweek.

Looks like the engine freedom issue may well be the huge (but not very effective) silencers I've always had on the car.

Saw for the first time at Mikes a fab 2.8 with PMO injection bodies....was that ever nice....injection! Mmmmmmmmmmmmmmmm

MikeB · Post by **MikeB** » Wed Jul 13, 2011 7:47 am

Graham

When Bob set the car up before, were the silencers off or fitted?

gridgway · Post by **gridgway** » Wed Jul 13, 2011 8:30 am

The silencers will have been on surely? You wouldn't set up an engine on a RR without the exhausts!

Graham

MikeB · Post by **MikeB** » Wed Jul 13, 2011 10:04 am

We found in single seaters if the racing silencers were fully packed it helped the engine. But it was a marginal difference. Frankly unless the inside tube of the silencer is distorting when in use, (Graham mentioned he could see through them when off the car) I'd be surprised if the silencers were stripping you of the 90 hp he suspects they are.

MikeB · Post by **MikeB** » Wed Jul 13, 2011 3:00 pm

Graham

Just trailed back through this thread to check out your silencers. I assumed that they were straight through jobs, but I see they are offset ones, which would have two perforated pipes inside them.

Obviously straight thrus would be better, but the short boxy silencers are to keep the ends are presumably within the rules.

Ho-Hum, nothing's ever easy, is it ??

911hillclimber · Post by **911hillclimber** » Wed Jul 13, 2011 6:12 pm

Nothing on this car is easy!

There is a perforated pipe diagonally through the oval section case of the silencer so you can see straight through it.
I bought them this length to get them inside the body so if i reversed/drove/skidded backwards I just might not damage them...

I hope it is somthing like this, at low revs the engine can breath but at 4K+ it starts to choke up so feeling 'dull' in response.

Discussed it with Bob and Mike last night when Mike was stripping the box. The fact that the tick-over rose from 1000 to 1600 is telling.

Today i have two 2" tubes to elongate the header stub pipes to the full length of the body. Doubt this will kill the noise much but just might help when the man checks the level at the first practice on the track. If too much i can simply put the silencers back on.

Gearbox will be done for friday this week. Mike has been ace.

Wish i could nick the engine with the PMO injection....

Bruce M · Post by **Bruce M** » Wed Jul 13, 2011 10:29 pm

I'd be surprised if a straight through silencer could choke the idle down. Could it have been the filters (restrictive as wet/dirty?).

If not... I'd be thinking the short manifolds with no back pressure might have changed the vacuum signature and improved the fuel/air balance. Up at 4k+ there is the possibility they are not flowing well so they might still be part of the problem.

One thing is certain.... There seems to a be a few ft/lbs left in the toolbox so it will worth getting it sorted out.

Good luck!