S2 Exige- lowering VVTL changeover?

[iguana]

Just curious after driving one & finding its absolute lack of power or torque pre changeover frustrating- is there a method- a la VTEC, of lowering the changeover point?

Cheers

[Sam_68]

Question is, would you want to?

Presumably Lotus and/or Toyota have set the changover to the optimum point between where the low speed profiles start to run out of breath and the high speed profiles start to come 'on cam'. Surely, altering the changeover point would just lead to a huge flat spot as the engine dropped 'off cam' by switching to the high speed profile before it had entered its working rev range?

Is there any scope for a 'hotter' low speed cam profile, so that the low speed torque (<2,500rpm, say) is sacrificed a little to give better breathing at the top of the 'low speed' cam range, hence less of a step as the high speed profile was switched in?

I stand to be corrected by someone who understads the Toyota VVTL system better, though...

[Stonie]

Try Piper Cams. Expensive though as they're billet cams, about £500 for the pair.

[bogie]

Piper cams for a Toyota engine?

...best bet is to get a supercharged car...much more flexible - Exige S ....or an Elise with Honda/Duratec/Audi ...all of which have more torque/more flexible

[junks]

May have some news on this soon - an ECU is being looked at as I type, there is already a place in the states that can alter the changeover point to around 4800 rpm.

I have no details on this thought until we get the remapped ECU

[cej]

if you feel there's a lack in power prior to the changeover,then it's probably set to high.
I tune a lot of Honda VTEC engined cars and when I set VTEC to the optimum rpm, it's no longer possible to feel a " VTEC kick" because the transition is so smooth. You are able to hear it though

[Stonie]

bogie,

Piper cams for a Toyota engine? ...Yes, thats right.

Take a look at their website in the cams section. They're listed for the Toyota Celica, part number VVTLIBP270 (fast road), 15bhp (stated) gain... but wouldn't know about any low end torque gain.

[bogie]

if they are anything like the fast road cams they do for the Rover then you will keep the same or lose a bit of torque low down...you cant generally have both...well thats what the VTEC/VVTI mechs are supposed to do - give you the best of both worlds

[S Works]

bogie said:

Piper cams for a Toyota engine? ...best bet is to get a supercharged car...much more flexible - Exige S ....or an Elise with Honda/Duratec/Audi ...all of which have more torque/more flexible

Agreed. The S is a revalation compared to the standard Exige. Am interested to go in an R and will be blagging a lift from Boggy tomorrow to see what it's like.

I had a pax in a Cup240 car this weekened (which is being run in so we couldn't use all the grunt) and that was superb, so much power. The unblown engine just never made sense to me, with the Exige S now available, it makes no sense at all in that car.

Here's to a blown Elise soon - that will be a great car.

[iguana]

Sam_68 said:

Question is, would you want to?

I don't own one, was merely curious & trying to talk a chum into one, but yeh if I did- I'd give it a shot, exige cracking car, but engine really is a torque free zone sub changeover & power band I feel is too small 'on cam'

S Works said:

The unblown engine just never made sense to me, with the Exige S now available, it makes no sense at all in that car.

Agree totally, driven em back to back & S is a far far better car engine is a gem, no milk float speed pre changeover & none of that tiny powerband malarky & at new price small price diference can't see why Lotus would ever sell another N/A exige again, but 2nd hand wise surely the non S prices will take a right hit tho- tho a good bet if a reasonably priced S/C kit comes along I guess.

[bobcorb]

I did some analysis on the S2000 cam profiles a while back it was very evident that the extreme profiles were going to give the pronounced torque peak at high speed. From the various SAE papers I looked at for data it appears that the S2000s low speed cams weren't that mild either so the torque was fairly competitive thru the mid range. By comparison the 2ZZGE engine has 228 degree low speed cams and only 7.6mm lift, also the exhaust manifold is very compact to minimise heat loss to allow it to pass EU4 emmisions without EGR (external) or secondary air - no wonder it feels strangled below 6000rpm. Now if the 2ZZGE engine were fitted with cams with ~260*10mm lift on the low cam and an optimised exhaust manifold I'm sure you could gain a really useful amount of low-midrange torque.

What I want to know is who asked Piper for the Toyota cams, and Janspeed for the exhaust? PTP are selling them but they dont market an ECU to control the whole thing. The ECU would be the icing on the cake. It would take forever to map an aftermarket ECU to suit the new cams/exhaust on a one-off basis. If there were a supplier who did the whole lot I'd be tempted. An S2 Exige with better midrange, another ~20BHP top end and none of the Exige S's extra 60kg - sounds v tempting and a lot cheaper than a blower.