57 replies to this topic

[Bigfella237]

Well done on the video mate, damn she certainly sounds nice at idle!

[orangeLJ]

Don't take a dyno.figure too seriously

Dynos are for tuning and comparing progress, not for determining how fast the car is.

Even the dyno dynamics shootout software (meant to make any run at any place comparable) is limited in its effectiveness.

Best way to see how fast it is would be the track

So don't stress about the power figure, just enjoy it

[LC-GTR-1969]

Ok finally some answers.

 

You were right orangeLJ, to take it to get put on a dyno was the correct thing to do, after I had got it running the best I could. This is important because if it was running too lean at high RPM apparently you can start welding pistons, not the best thing for a brand new engine. So I recommend this to anybody who has just built a new engine. I didn't know, and a dyno is the only way to be sure. 

 

The outcome of the dyno was that the carbs are set up fine, and all the emission figures are within spec. Its not running too lean or too rich.

 

I then took it to another carb specialist for a second opinion who immediately asked where my vac advance was. Now, the first guy told me that I didn't need a vac advance because it only helps with fuel efficiency. However this guy reckons that this is what is causing the hesitation at initial throttle.

 

So, he told me to advance my timing (which is currently set at 12BTDC) by 5 deg and see if it fixes the issue. It did, not completely, but it certainly made a difference.

 

The reason I didn't have my vac advance set up is that my triple webers did not come with vac advance as an option. It looks like you have to drill new holes in the carbs, which all seems a bit strange.

 

Anyway, she's putting down 83kw on the ground which isn't much, but not too bad for a little 186.

 

Thanks for all the help on this thread, I really appreciate it.

 

Do you have any engine specs? What cam is it running? Head- is it 9 port or 12 port? Is it ported? Also, do you have any idea what compression ratio the engine was built with?

 

If you can track down this info it would really help us with helping you get the best set-up... You don't need vac advance, however you may need to get your distributor re-graphed to suit the cam as well as the engine compression. If you just give the engine more initial advance at idle, you will also be giving the engine more total advance, which if too much can cause real issues with detonation and melted pistons etc...

 

For example, 12'BTDC at idle is about right for a mild set-up, with between 32-34 total (again for mild set-up)- a bigger cam will probably want more initial timing (like 16-18) depending on the compression ratio and about 32 total timing...

 

If you can find more specs we should be able to point you in the right direction!

Edited by LC-GTR-1969, 02 February 2015 - 04:35 PM.