20 replies to this topic

[Project_1275_GT]

Hi 

 

Hopefully someone can point me in the right direction with this. I am building a 998 Turbo and intend to use the 65DM4 distributor. I know there are many benefits of using more modern tech in this area but my build is trying to remain original parts where possible. 

 

I have read plenty on distributors and believe the advance curve must be quicker than standard and not as much, normally this is done by changing springs and restricting the movement [weld added]. I also understand that this is probably best done after a RR session to determined what is required. 

 

Can anyone give suggestions to knowledgeable people able to modify distributors correctly? Has anyone previously done this and able to give some advice on requirements? 

 

Thanks

 

Rob

[cal844]

AC Dodd is your man here, no doubt he will be along soon with advice

[sonscar]

Have you thought how you are going to reference the advance to boost?I have no experience with boosted dissys only using mapped ignition so am curious.Steve..

[ACDodd]

Modifying the dizzy is easy! Knowing the exact advance curve for your spec is the impossible bit!

The way to do this is to modify the dizzy to a safe curve, dyno the engine to work out its exact needs, then modify the unit again to match these requirements.

Ac

[Project_1275_GT]

Modifying the dizzy is easy! Knowing the exact advance curve for your spec is the impossible bit!

The way to do this is to modify the dizzy to a safe curve, dyno the engine to work out its exact needs, then modify the unit again to match these requirements.

Ac

 

My plan at the min is to leave the springs alone and restrict max advance. I have tried to research it but as you say its impossible to know. How much to restrict advance is also difficult to know. Near every bit of info i have read indicates 3mm weld. Might see if i can come up with something other than weld. 

 

Drive with caution when built and get to a dyno ASAP. 

 

Thanks

 

Rob

[dyshipfakta]

Metro turbo dizzy would be safe but curve not right

[Project_1275_GT]

Metro turbo dizzy would be safe but curve not right

 

The 65DM4 is the correct dizzy for later metro turbo. Was also used on other engines later on. I don't think there is any difference between any 65DM4 units. So its a reasonable start point but defiantly not correct. As I say I am pretty certain it will require less advance so I will make adjustments to the stops and hopefully that will get it going ok. 

[cal844]

Metro turbo dizzy would be safe but curve not right

The 65DM4 is the correct dizzy for later metro turbo. Was also used on other engines later on. I don't think there is any difference between any 65DM4 units. So its a reasonable start point but defiantly not correct. As I say I am pretty certain it will require less advance so I will make adjustments to the stops and hopefully that will get it going ok.

The car will drive ok on the road, however there are many different advance curves from the factory.

[Project_1275_GT]

 

 

Metro turbo dizzy would be safe but curve not right

The 65DM4 is the correct dizzy for later metro turbo. Was also used on other engines later on. I don't think there is any difference between any 65DM4 units. So its a reasonable start point but defiantly not correct. As I say I am pretty certain it will require less advance so I will make adjustments to the stops and hopefully that will get it going ok.

The car will drive ok on the road, however there are many different advance curves from the factory.

 

 

So there is more than 1 curve used in 65DM4? I thought they were all the same unit? 

[GT Jimmy]

just a thought, I've got a CSI electronic dizzy in the GT, it has 16 different advance curves that are set with a small philips

screwdriver, just a matter of popping the cap off to change the setting. Might be worth a look at

[Project_1275_GT]

just a thought, I've got a CSI electronic dizzy in the GT, it has 16 different advance curves that are set with a small philips

screwdriver, just a matter of popping the cap off to change the setting. Might be worth a look at

 

I may look at other options for this engine. The obvious choice is to use use modern tech to program the correct advance. But I really am trying to stick with as many genuine parts as i can.

 

I will do some reading on CSI as its still a distributor. 

[timmy850]

You can use something like this. You disable your mechanical advance, and then program the required advance against rpm and vacuum/boost. It essentially just uses the distributor as a crank angle sensor and then the black box sends the signal to the coil to fire the spark

https://www.cbperfor...dule-p/2013.htm

[Turbo Phil]

If you're going to the expense of a new distributor, you're far better off looking at a programmable ECU. Even a basic ECU is far superior to some clockwork dizzy. 
If you're set on using a dizzy, though far from ideal, why not remove the advance springs and fix the advance mechanism with weld. Then adjust the timing to be safe under your maximum boost level, but retain the vacuum advance unit to improve bottom end. 

 

Phil. 

[Project_1275_GT]

If you're going to the expense of a new distributor, you're far better off looking at a programmable ECU. Even a basic ECU is far superior to some clockwork dizzy. 
If you're set on using a dizzy, though far from ideal, why not remove the advance springs and fix the advance mechanism with weld. Then adjust the timing to be safe under your maximum boost level, but retain the vacuum advance unit to improve bottom end. 

 

Phil. 

 

I have been doing some reading on ECU systems, I'm still trying to resist at the min. 

 

So your saying removing springs and using a fixed advance would be better that restricting max advance? 

[cal844]

Metro turbo dizzy would be safe but curve not right

The 65DM4 is the correct dizzy for later metro turbo. Was also used on other engines later on. I don't think there is any difference between any 65DM4 units. So its a reasonable start point but defiantly not correct. As I say I am pretty certain it will require less advance so I will make adjustments to the stops and hopefully that will get it going ok.

The car will drive ok on the road, however there are many different advance curves from the factory.

So there is more than 1 curve used in 65DM4? I thought they were all the same unit?

They are the same unit but as with any engine the advance curve will be different for each engine and also depending on spec (sprite to Cooper as an example)