bad acceleration?
Discussion
I'm a bit concerned about my S2:
Its a bit week below 2k rpm, how is it supposed to feel? I've adjusted the timing so it now gives 30 degrees btdc over 3k rpm (euro spec) and now it feels acceptable but no more.
How does your S1 & S2 cars feel in low register?
I have rebuilded the carbs & the distributor, so everything should be ok, what should I expect from the S2 Esprit in term of acceleration from low revs?
BR
Anders
79 S2
Sweden
Its a bit week below 2k rpm, how is it supposed to feel? I've adjusted the timing so it now gives 30 degrees btdc over 3k rpm (euro spec) and now it feels acceptable but no more.
How does your S1 & S2 cars feel in low register?
I have rebuilded the carbs & the distributor, so everything should be ok, what should I expect from the S2 Esprit in term of acceleration from low revs?
BR
Anders
79 S2
Sweden
Hi,
What you describe is very subjective. A lot depends upon your level of expectation. Traditionally, all 4 cyl. lack low-end grunt, and in the NA Esprits, there isn't all that much to spare. If the car goes well 'on cam', then what you're experiencing is normal and one of the reasons Lotus upgraded to Turbocharging the 9XX engine.
Everything is relative and when introduced, it more than held it's own. But, when compared to modern 4-cyl. cars with Forged Pistons, EFI, Vario-Cams, improved Exhaust systems, etc., the NA Esprit is showing it's age. You may be making these kinds of comparisons subconsciously.
Happy Motoring! ...Jim'99 Boxster
What you describe is very subjective. A lot depends upon your level of expectation. Traditionally, all 4 cyl. lack low-end grunt, and in the NA Esprits, there isn't all that much to spare. If the car goes well 'on cam', then what you're experiencing is normal and one of the reasons Lotus upgraded to Turbocharging the 9XX engine.
Everything is relative and when introduced, it more than held it's own. But, when compared to modern 4-cyl. cars with Forged Pistons, EFI, Vario-Cams, improved Exhaust systems, etc., the NA Esprit is showing it's age. You may be making these kinds of comparisons subconsciously.
Happy Motoring! ...Jim'99 Boxster
be carful messing with the advance, to much can lead to engine damge best to be very conservative when increasing this, as for power i have an excel which basically has the n/a esprit engine and its a very 2 sided engine less than 3.5 on the rev counter an its no more powerful than most ordinary cars complete with flat spots etc etc all the carbed 912's were like this once you get past 3500 the engine pulls well all the way to 7000 rpm if you keep the engine in the 3500 an above zone all the time the car's quite fast an picks up speed quite quickly but this is not pratical to do unfortnatly so you'l have to get used to the low end weakness an accpet that whenever you want to acelerate quickly you'l have to drop a gear
on a side note i beleive that most 16v 4 cyclinder engines from this time frame porsche, bmw etc were similar not really comming alive till high rpm's there's no doubt that todays 16v 4 cyclinder cars are much more flexible
theres been a lot of talk about the engine on the excel forum and i'm sure this will be true for the n/a esprits aswell the consensus is that a couple of degrees more advance a decent induction system taking cold air from outside the car and rejetting the carbs with slightly larger idle jetts improve the engine all round especially the low end an make town driving easer
on a side note i beleive that most 16v 4 cyclinder engines from this time frame porsche, bmw etc were similar not really comming alive till high rpm's there's no doubt that todays 16v 4 cyclinder cars are much more flexible
theres been a lot of talk about the engine on the excel forum and i'm sure this will be true for the n/a esprits aswell the consensus is that a couple of degrees more advance a decent induction system taking cold air from outside the car and rejetting the carbs with slightly larger idle jetts improve the engine all round especially the low end an make town driving easer
Hi Anders,
They're all weak below 2000 rpm. The 907 was known to be pretty short on torque, and what it did have didn't come on until higher in the rev range. Don't expect to have much real fun at less than 3500 rpm, and get comfortable with the idea of bouncing off the rev limiter regularly. Use the gear lever and keep the revs up.
At least you have the higher compression ratio and the E-cams. In the USA we got the low compression and the C-cams for even less low-end grunt.
The Excel that Peter mentioned had the 2.2 liter 912 engine. The small increase in displacement may not seem like much, but it makes a very big difference in low-end torque. If you want a stronger engine, the best thing you can do to your 907 is stroke it to 2.2 liters. The 2.2 is still at it's best above 3500-4000 rpm, but at least it doesn't feel anemic at low speeds.
The 9XX engines like ignition advance and you're in the ball park now at 30° BTDC. As long as the local fuel's octane rating can support that much advance and the engine doesn't ping, then more is better up to about 32° BTDC. I routinely run more total advance than that (as high as 40°), but my engine is not stock. I wouldn't recommend that you go with more 32° total advance without careful consideration and testing.
Make sure the cam timing is correct and hasn't jumped a tooth. When the cam timing is off, the engine really gets weak and the car can barely get out of it's own way.
Keep the revs up…
Tim Engel
They're all weak below 2000 rpm. The 907 was known to be pretty short on torque, and what it did have didn't come on until higher in the rev range. Don't expect to have much real fun at less than 3500 rpm, and get comfortable with the idea of bouncing off the rev limiter regularly. Use the gear lever and keep the revs up.
At least you have the higher compression ratio and the E-cams. In the USA we got the low compression and the C-cams for even less low-end grunt.
The Excel that Peter mentioned had the 2.2 liter 912 engine. The small increase in displacement may not seem like much, but it makes a very big difference in low-end torque. If you want a stronger engine, the best thing you can do to your 907 is stroke it to 2.2 liters. The 2.2 is still at it's best above 3500-4000 rpm, but at least it doesn't feel anemic at low speeds.
The 9XX engines like ignition advance and you're in the ball park now at 30° BTDC. As long as the local fuel's octane rating can support that much advance and the engine doesn't ping, then more is better up to about 32° BTDC. I routinely run more total advance than that (as high as 40°), but my engine is not stock. I wouldn't recommend that you go with more 32° total advance without careful consideration and testing.
Make sure the cam timing is correct and hasn't jumped a tooth. When the cam timing is off, the engine really gets weak and the car can barely get out of it's own way.
Keep the revs up…
Tim Engel
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