Salt Flash....An A10 for Bonneville.

[Briz]

Well, we got a good deal done this weekend. About half a dozen small tasks to do before we try fireup.
Some pics:

[muskrat]

Looks fast just sitting there Briz.
Please have someone video the start up (warts an' all). I have t' hear it roar.
Cheers

[Briz]

The last week has had its ups & downs to say the least!
Got it started for the first time on Wednesday and booked dyno time on Friday.
Abortive.
Basically, Amal carbs are not suited to being pump-fed. And we need fuel pressure to stay ahead of boost pressure.
We took the 4mm float needle-seats out and put in 2mm ones, remachined the bowls to get more float movement and set the fuel level lower, but it still ***** out methanol with the pump running. Even at minimal 0.5psi pressure.
In the end we decided to run the pump thru the kill switch alone so we can use it to prime, then shut it off whilst idling and only turn it on when underway.
http://youtu.be/Fc4q4Z7JDR0

[JulianM]

Hi,
Try fitting a boots sensitive fuel pressure regulator before the floats, then feed the float bowls with boost through their breathers, that way your needle valve will only ever have to deal with the initial set fuel pressure as it will now work on the differential between internal air pressure and pump pressure which will both now be altering in unison. Worked for me on many occasion.

Best regards,
Julian

[Briz]

Thats exactly the setup we have Julian.

[JulianM]

Sounds like you have a problem then Briz 

I know it's a little late now for change but if you keep having problems the following may be interesting for you.

Many moons ago when we were experimenting with a Methanol powered 1500cc Supercharged pre-war race engine we found that if we ran a big SU on the inlet side of the blower (or turbo in your case) we got a much better power output than running "blow through"  this we concluded was due to the high latent heat of vaporisation of the Methanol being given time to "do it's job" by cooling not only the intake charge directly but it actually cooled the blower unit so well that we were getting heavy condensation buildup on the outside of the blower its self.  When run with blow through the blower got very hot and power was hit substantially. Even worse, when run on petrol with this setup the blower was so hot it caused many problems that limited boost and power enormously.
Not only this but the engine was a lot less sensitive to mixture and ran within 2% of max power from lambda 0.85 to 0.65 which is extremely rich indeed! We put this down to better atomisation "through the blender"   You also completely do away with the need for the intercooler and associated long pipework / weight.
If you are worried about the turbo not handling vacuum then you can run a butterfly up by the head and the carb back at the turbo inlet, this works fine but you will need a "wet" blowoff valve to stop surge when shutting off the throttle.

Good luck anyway, the bike is looking really great!!
Julian

[unclerob]

Hi Briz, have been admiring your work for a while now and hope you manage to sort the fuel issue and make it to Bonneville! I used to build racing cars once and well remember how it feels to struggle with problems like that with a deadline looming....
I hesitate to offer any advice (mainly because I don't really know enough about this kind of thing!) but I am thinking that the Amal floats simply aren't large enough to shut off anything but minimal pressure....so for what its worth (not a lot probably!!) heres a couple of thoughts....remote floats (big SU maybe?) on adjustable mounts and do away with the Amal ones but keeping the carbs as is?....or some sort of overflow/return system feeding back to the tank...or a catch tank? Both bodges I know but just a thought....
Best of luck

[Briz]

Thats exactly the problem UncleRob. Amal floats are too small for this kind of thing. The remote float idea is a good one, one of the guys on Landracer posted a pic of something similar using a Holley float bowl, which is capable of dealing with up to 5psi. Thats what we'll do after we come back.
An overflow-return wont work on pressurised carbs.
Either that or we'll switch classes to non-vintage and go EFI. The class record for pushrod/ fuel is only 7mph faster than vintage.
Julian; everybody I've spoken to about carb'd turbos is of the same opinion....suck-thru sucks!

[JulianM]

Hi Briz,

Totally agree, everyone we spoke to also told us the same,  However after research we found that most had not even tried it and if they had it was with petrol. And in that case they were absolutely correct.  The Methanol though was a different world! 
I was working on Turbos in 1981 when they first started to be the "dish of the day" and the amount of people who told me it could not be done or it doesn't work would have made me rich at a penny for every one.   
I'm not saying change the lot for one minute as your bike looks great.  I am just saying that if you start to hit real issues then it's worth a consideration.  Blowing through carbs for high boost is not easy and the jetting can be a real pig!

Best regards
Julian

[JulianM]

Just a thought!

How about a Gardiner carb (or two) which are basically designed to flood at anything over half throttle anyway.  May prove the perfect answer.

Julian

[Briz]

I like the car float idea best. We got a pair of deep floats thru from Amal yesterday. We'll try these.
But the bike is in the hands of the shippers now, so its all down to the salt now.

[JulianM]

Hi Briz,

Hope you don't mind all the suggestions as I have another one for you   

This one does work and has been tested but no idea if it will work on your setup.  could be sorted on the lake though, hence the reason for posting.

If you do away with the fuel pump, run large float jets and run a pressurised fuel tank, (boost into the fuel tank breather and float bowls) it should in theory only give Gravity over float bowl pressure.

Good luck and come back with a record or at least a big smile!!

Julian

[Briz]

Right! We're flying off to the salt tomorrow morning. Speed week starts next Saturday. We'll try to keep you posted of our progress...or otherwise!

[muskrat]

Best of British luck to you Briz.
Cheers

[duTch]

  .......Best of Aussie luck too...