Ignition retard

[ranj]

I need to retard my ignition timing so that i can make 20psi with a gt28r without detonation occurring .... I know bb tuning when they existed used to sell tdc sensors with 6 deg retard on them .... but i cant find them anywhere now ..... CGB sell em but with 6deg advance only ..... Anyone Help me ???

Also does anywhere still sell the adjustable timing sensor if i cant get the above ..... Cheers.

[paul b]

you already have one.....
pop yours between the (loose) jaws of a vice and tap it.....move 1 and half holes...each hole is 4 degress, reglue in position...job done...

or did I make that too simple....LOL...

remove the word ignition from the post title...thats me that is...LMAO

[Sparkie]

I need a retard .... but i cant find them anywhere now ..... Anyone Help me ???.
:laugh::laugh::laugh:

you need a vice or couple of bricks. - place the jaws or the bricks slightly apart so you can slip the metal part of the bracket down between the gap.
get a go-gas gun and heat the metal bracket until the plastic on the sensor part starts to bubble - then tap the bracket out of the melted plastic sensor.
use a file, to get rid of the protruding nobble on the bracket - clean off the melted plastic and slide it back into the sensor unit.
voila, adjustable sensor.

[Alex]

I'm quite surprised it's knocking at that boost pressure? What AFR is it running Ranj? Charge cooling temps o.k.?

[Mart]

I'm quite surprised it's knocking at that boost pressure? What AFR is it running Ranj? Charge cooling temps o.k.?

Unless it's running a high(er) c/r and/or 95ron fuel.

If not though, agreed, 6deg' retard is overkill for 20psi.

[ranj]

I have detonated the engine twice ... both times killing the pistons in cylinder 1 .... i havent heard the detonation myself but it must be happening as the pistons have melted both times ...... the afrs are spot on .... i have checked them twice with 2 gauges .... first a lc1 and then a lm2 .... the afr didnt go over 12.0 when on WOT and charge air temps were fine too as i have a gauge for measuring them too .....but still the piston melted ........ The pinking sensor should have retarded the igntion timing by 6 degrees ..... Its always been run on shell optimax or tesco 99ron.


SO before i put it together again this time i measured the head and it was 73mm ...... a few words with scoff and it seems it on the limits at 20psi .... and detonation was definately the cause of the problem .... so to stop it i would have to retard the ignition ... but by how much i really dont know yet .... was gonna start at 6deg .... turn boost up on rollers with det cans and see how high i could take the boost before detting occurs .... if it happens after 20psi then maybe i could reduce the timing to 4deg retard or less .... but i really need to be safe as possible as i dont fancy a 3rd build in 2 months ......... :)

[Jono]

Hi Ranj ,I melted a piston at just 18psi of boost. ( with a T25 and double capacity intercooler) AFRS we low 12s. Head was 73mm. I had a quick chat with Scoff at the time and he suggested checking that the AEI module. I have not quite got mine back together get so I have not had chance to do it. ( but I will lol) I was planning on following your route and making up some det cans ( i didnt hear the detonation either )and starting at 14 psi and go from their. To be fair I was only running 95 octane fuel too which maybe/probably contributed.

[FQ200turbo]

using this post :rolleyes:...
any opinion for a 21psi T25 turbo, stock cam, front mount, group a carb with 98 fuel, this for a 1/4mile car :cool:

[rs250nut]

using this post :rolleyes:...
any opinion for a 21psi T25 turbo, stock cam, front mount, group a carb with 98 fuel, this for a 1/4mile car :cool:

Ive got a group B carb on mine:coffee:

[ranj]

OK .. managed to get the tdc sensor moving on the metal bar ... Each hole is 4 degrees .... so am i right in thinking that it is both upper and lower holes .... so lower hole is 4degs then upper is 8degs and so on ... Im gonna use split pins in holes tp stop it moving about and glue too .... whats best glue to use ??

[Sparkie]

how is it gonna move- its not touching the flywheel....

[ranj]

Just thought it may move by vibration ....

[THE MASTER]

a liitle tip . when bashing the pick up plate put an 8mm drill in the hole of the plate . (were the mounting bolt goes through) this stops the plate distorting
also if there is any leaks in the vac pipe from the manifold to the aei that will also afect your timming . so if you have a d/d/d/d/dump valve make sure its sealed and working propperly
;)