Discussion
Hi,
There is a marginally infamaous flat spot around 3K RPM on the 9XX engine. It is a combination of factors which cause it and the carbs are one of these. It's effects are most strongly felt in the lower gears.
Just as the cause is multi-faceted, so is it's solution. On carb'd cars, the best (greatest benefit from cost/labor) fixes are rejetting the carb's idle jets to a richer jet (aids in the transition to the mains), running a 104° M.O.P., dialing in more advance (<30°, but >12°), adding a slightly higher lift cam (104 Cam is excellent). These will mitigate the issue so that it's manageable, but eliminating it totally is expensive and not generally worth the effort. Happy Motoring! Jim'85TE
There is a marginally infamaous flat spot around 3K RPM on the 9XX engine. It is a combination of factors which cause it and the carbs are one of these. It's effects are most strongly felt in the lower gears.
Just as the cause is multi-faceted, so is it's solution. On carb'd cars, the best (greatest benefit from cost/labor) fixes are rejetting the carb's idle jets to a richer jet (aids in the transition to the mains), running a 104° M.O.P., dialing in more advance (<30°, but >12°), adding a slightly higher lift cam (104 Cam is excellent). These will mitigate the issue so that it's manageable, but eliminating it totally is expensive and not generally worth the effort. Happy Motoring! Jim'85TE
lotire said:
has anybody got any experience of a flat spot just when you accelerate from take off slowly in 1st on my car "dellortos Stevens model". It doesn't happen when you really accelerate hard just on nice and easy acceleration you kinda have to slip the clutch a little to get her going
I've noticed this aswell, especially if using standard unleaded fuel. The engine tuning is the next thing on my list of jobs so 'Jim', I guess I'll be speaking with you more often. I seem to recall you mentionng about 104Deg. I have 'Green Dots' are these what you are talking about.
Do you know if the 104's are standard or could it an upgrade from an PO. Also has anyone published this info along with cam replacements, Piston upgrade etc. I have info on Water injection, Chargecooloer, Dump Valves and increasing bost but nothing on replacing/Upgrading engine parts.
Steve
89 Turbo
Steve
89 Turbo
unity1 said:
Do you know if the 104's are standard or could it an upgrade from an PO. Also has anyone published this info along with cam replacements, Piston upgrade etc. I have info on Water injection, Chargecooloer, Dump Valves and increasing bost but nothing on replacing/Upgrading engine parts.
Steve
89 Turbo
Luckily, Tim Engel has just posted a couple of superb spreadsheets with cam and pulley data from the first 907's up to the last 910's. See:
http://groups.yahoo.com/group/turboesprit/files/tech/engine/
You will probably have to join the group if you haven't already. Alternatively, drop me a line and I can e-mail it to you next week sometime.
Cheers,
Sanj
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