Sizes Verification

[knights_templar]

so owning SR. what are you qualifications, engineering, mechanical, design?

[marlin]

Rambles are good, keeps the natives bored. Even if I did have to google 'off piste'.

 

Rev limiter set at 5500, even though I do bump it occasionally and have to remember "what was that?". Limited fund so don't want to break my toy.

 

Only have seen photos of your cars. The DAX is something else. Chevy in a cobra, tisk, tisk, loss of another over to the darkside.

429 FE, dry sump? Is he planning on pulling stumps out of the ground with that torque? $$$,£££ That is one fun hobby to have.

 

Back to present build; HP pump failure on install/test yesterday. Come to find out no warranty on Walbro pumps. Share the knowledge of my unfortunate discovery. New one on order. System seemed to hold 60 psi for a while before pump death.

[Guest lotusPaul]

Knights,

Sorry about that.i meant ive owned an SR. In fact several. Almost brought the company from the brothers. My Father and I used to build them alot. Very simmilar to the Brian Annals/ Dax relationship of the 80s/90s.

 

My quals are degree in mechanical engineering from Lancaster uni, amounst overs. Job wise, now retired but spent 24 years almost as a Military Royal Engineer. Specialist in Tank mechanics. I looked after the Army race bikes and race cars too.

 

I have a love and passion for engines that extends far beyond what most would consider normal.

[Guest lotusPaul]

Marlin,

 

At 5500 and 85% ve your only needing less than 415cfm flow. So by going to big on the carb your slowing down velocity, this in turn will not be letting the suspended guel to atomise correctly. You then have to richen it up, gas millage drops.

This is a prime situation where the standard Ford Autolite stock carb will be apsolutley fine. Too much cam will also compound the effects.

[WallerZ]

To go back to your original question Marlin, I'd stick 1840cc in and have done. Its common that MX5 engines get rebored and used on the stock ECU. As you mentioned, you will be monitoring and driving parameters from you AFR, MAP and TPS rather than cc. Having that rebore and a few cc missing from the ECU isn't going to harm you

[marlin]

lotusPaul;

Yes, over carb is a problem with the male species. I didn't want to go to a 2 barrel carb but did add a phenolic spacer to help increase the velocity, as I understand, and help prevent any heat soaking of the carb. Lucky for me I was still able to fit the taller Holley, under the bonnet with my 3" air cleaner. Just barely. I used the mustang convertible motor mounts which sit a bit lower than the tin top mounts.

 

WallerZ;

Thanks for pulling us back on topic. I will check with the Haltech tech when he gets back from holiday whether the number makes any difference and/or what number I should use. Will report back results.

 

Thanks all,

Marlin

[Guest lotusPaul]

Those spacers do not help you in your aplication. It does issolate from heat, True.

But, it increases the size of the plenum chamber. A large plenum will stall the air at low openings, but allow high velocities at higher revs. A small plenum does exactly the opposite, it allows much higher velocities at low openings but does restrict flow at the top end.

 

So now were into two mismatched components which is not helping your fuel attomisation, and without question causing fuel drop out. Also quite probably throttle response in the first 80ft.

[marlin]

Well then I will remove it and allow for better fit of air cleaner. Assuming no lower clearance issues. More concerned with low end performance than top end. How often are we at the top end anyway?

Thanks for the education. Knew there was a reason I joined up with this bunch.

[Guest lotusPaul]

To save ruining this thread, if you mail me with your specs id be happy to suggest some changes.

[marlin]

Thread conclusion: From Haltech tech center. The duck and others you were correct.

 

"The Volumetric Efficiency calculation does use engine capacity. You may change it in the main setup. It will make little difference."