The Lotus Cars Community banner

1 - 13 of 13 Posts

·
Registered
Joined
·
913 Posts
Discussion Starter #1
Im due to replace my timing belt, and the guy that inspects my Esprit is pretty good with exotic cars. I always see Porsches, Mercedes, and other high end cars at his shop whenever im there or drive past. And he can talk KJetronic like the Bosch book. He was telling me that the cam timing on my Esprit could be adjusted to greatly reduce the turbo lag that it has presently. My question is, do I have to necessarily buy green dot pulleys or is it possible to tweak the cam timing to create this gain in low end driveability? I was thinking upon doing my belt, maybe I could adjust the cam timing if there was a "modified" position for the existing cam gears when doing so, or if the green dot pulleys are a necessity, like maybe they are a different size or number of teeth.
 

·
Integrator
Joined
·
2,862 Posts

·
Wingless Wonder
1988 Esprit Turbo
Joined
·
6,088 Posts
Just to clarify,

The Jack Shaft is called the Auxilary Shaft in the Lotus books.

It's the cam wheel that drives the distributor.
 

·
Registered
Joined
·
480 Posts
All the cam wheels have the same number of teeth, just the keyway is in different position.

Stock timing is 100 degrees exhaust, 110 intake.

Green wheels are 104 degree, which is what the cams were designed to be run at (104 degrees at maximum opening point (mop)).

The 100 degree stock pulley (blue) is actually supposed to be 97 degrees, so the exhaust cam is retarded 7 degrees, with the intake being retarded 6 degrees, both for pollution purposes.

The green dot pulleys will help on low end torque, most evident when off the turbo.

If you do not buy an additional pulley, just swap the aux shaft green dot pulley with the red intake pulley, and that will help for free. Doubt you will feel much of a difference on lag or spool up.

Brian
 

·
Registered
Joined
·
860 Posts
you get a slightly lopier idle....and off idle torque is improved. You lose a little top end though. Essentially, you are just shifting the power curve a few hundred rpms "to the left."
 

·
Registered
Joined
·
913 Posts
Discussion Starter #6
So I could actually calculate the difference in degrees using the stock pulley setup, and just remove the belt, figure out where it is at presently, then plus or minus the degrees increments, then remark my pulleys where the new setting would be. Or an even easier way to do this would be to create the mark using my existing distributor pulley since it sounds like there is not a difference in the exhaust and intake pulleys with the green dot versus the pulleys the car has now other than the dot being in a different spot and green? I could just line up the keyways, make sure I have the front to back of the pulley correct and mark it and not purchase any pulleys. Then just swap one of my pulleys to the distributor.
Believe it or not the distributor pulley is the one that I hate messing with, when I bought my car I had hard time getting that pulley at the point where the vacuum advance wasnt up against the engine block and allowed for proper timing adjustment. Oh to have electronic ignition.
This sounds like cheap way to rid turbo lag, if it works LOL. Worst case scenario im back on here next weekend looking for cylinder head valve components right.
 

·
Registered
Joined
·
860 Posts
I think there are 40 teeth on each cog. considering that the cam pullies move at half the crank speed, a complete revolution on the cam sprocket represents 720* of crank rotation. that being said, advancing each cam sprocket one tooth would equate to a 18 degree movement relative to the crank........

assuming I did my math correctly, you don't want to go that route!
 

·
Registered
Joined
·
124 Posts
So I could actually calculate the difference in degrees using the stock pulley setup, and just remove the belt, figure out where it is at presently, then plus or minus the degrees increments, then remark my pulleys where the new setting would be. Or an even easier way to do this would be to create the mark using my existing distributor pulley since it sounds like there is not a difference in the exhaust and intake pulleys with the green dot versus the pulleys the car has now other than the dot being in a different spot and green? I could just line up the keyways, make sure I have the front to back of the pulley correct and mark it and not purchase any pulleys. Then just swap one of my pulleys to the distributor.
Believe it or not the distributor pulley is the one that I hate messing with, when I bought my car I had hard time getting that pulley at the point where the vacuum advance wasnt up against the engine block and allowed for proper timing adjustment. Oh to have electronic ignition.
This sounds like cheap way to rid turbo lag, if it works LOL. Worst case scenario im back on here next weekend looking for cylinder head valve components right.
Just swap the green dot pulley from the distributor shaft for your intake pulley, line up the pulley dots on intake/exhaust just like the manual (although one dot will be different color now) and your done, don't over complicate it. As long as you don't move your dist pulley shaft to any great degree before installing the old intake pulley on it then it shouldn't be hard to retime it, just slight tweaking of the distributor if any, I did this years ago on my 83 and it does allow the engine to breathe Better thus giving it more overall oomph (seat of the pants term) especially in the lower end, so I do believe that equates to feeling like slightly less turbo lag...you can also advance your timing which really makes the car come alive. my 83 is set at around 16btdc static with carbs..the difference is night and day compared to the joke emissions timing...then your most of the way to euro spec (advanced timing and pulley swap).

Dave D. 83 Turbo Esprit
 

·
Wingless Wonder
1988 Esprit Turbo
Joined
·
6,088 Posts
you can also advance your timing which really makes the car come alive. my 83 is set at around 16btdc static with carbs.
Mark, I agree with this... If you don't know the spec for Bosch FI dizzies, I'll look it up tonight. (I think it's 17 - 18BTDC)
 

·
Registered
Joined
·
1,886 Posts
you get a slightly lopier idle....and off idle torque is improved. You lose a little top end though. Essentially, you are just shifting the power curve a few hundred rpms "to the left."
Yep - thats what you "get". It does make a difference though. Power available at more usable RPMs always beats out power when shes revved out.

Mark, I agree with this... If you don't know the spec for Bosch FI dizzies, I'll look it up tonight. (I think it's 17 - 18BTDC)
For the record, my cars timing is set at 15 deg BTDC. The factory spec says 22 deg but my car runs great at the 15 deg. The original owner set it that way after experimenting. This is a 1987 HCi, BTW.
 

·
Wingless Wonder
1988 Esprit Turbo
Joined
·
6,088 Posts
For the record, my cars timing is set at 15 deg BTDC. The factory spec says 22 deg but my car runs great at the 15 deg. The original owner set it that way after experimenting. This is a 1987 HCi, BTW.
OK, have looked up the specs set forth by Arnie Johnson at LOG 19. :bow:

For Bosch FI Esprits, he recommended 15 - 18 degrees BTDC, at warm idle.
 

·
Registered
Joined
·
1,886 Posts
OK, have looked up the specs set forth by Arnie Johnson at LOG 19. :bow:

For Bosch FI Esprits, he recommended 15 - 18 degrees BTDC, at warm idle.
Hmmm - OK. My previous owner(Tom) said after a major it was set to 22 deg but he felt the car ran weird and messed with it himself and settled on 15 deg.

Either way - yeah, find that sweet spot and go with it :)
 

·
Registered
Joined
·
136 Posts
I had green dots installed during my recent rebuild and I LOVE them. Much better performance from a stop (doesn't feel like it is going to stall) and off boost. It does sound a bit more "loapier". Here is the 2nd running of my new engine with them. I have about 200 miles on it now and really enjoy the drive-ability with the green dots.

By the way, in case your wondering... it won't start with the cam gears on backwards.. and more importantly doesn't cause any valve damage.

 
1 - 13 of 13 Posts
Top