Lowering cam changeover on VTEC/VVTI engines

eidolon · 19 Aug 2006 at 08:31

I know that Merlin has had this done on his Teg but does anyone know of any Celica owners that have done the same thing.

It appears that Lotus have locked the ECU on the Elise so I don't think that there are any UK owners that have been able to mess with it however Ragnorak Racing offer 230BHP upgrades which include a reflashed ECU over in the US so I don't imagine it will be long before this mod hits our shores.

What are the downsides of lowering the changeover? Surely if it's just an ECU reflash then Lotus would've done this as standard wouldn't they?

Ragnorak also offer a 280BHP upgrade (turbocharged) which lowers the changeover down to 4000rpm, how is it possible to lower it so far? Is it due to the turbocharging?

Bear · 19 Aug 2006 at 09:11

I would guess its possible to set the change over point to pretty much anywhere you want within reason so long as there is enough oil pressure to do so. I would have thought once there is enough oil pressure, there would be a solenoid which actions the change over which is set to a certain revs.

Apart from possible lower mpg, I guess you would have to look at the power plots and see when the cam is switched over, the response of the other cam would maintain a decent curve. Move the change over point too low then you would end up losing low end power as the high cam is meant for power higher up the rev range. All a guess though.

Oxbow · 19 Aug 2006 at 09:27

Could you not just replace the ECU with a Toytoa item and fettle with that?. ECUs really are not as scary as people make out. Simple software and a knowledge of electronics can get past most ECU 'Locks' with ease.

Regarding the changeover, Bear is correct in saying that as long as the oil pressure is there (which it will be as its a constant in modern engines), you could have it pretty much anywhere you wanted.

I would imagine its 4k rpm with the TC in order to make the maximum of the torque band that a turbo offers. Higher up in the rev range on a turbo, and the TC starts to restrict the car rather than aid it.

realscot · 19 Aug 2006 at 10:05

Honda's can get a Vtec controler, allowing you to change the revs the vtec comes in. I don't personally have one on mine, but I know people that have taken their vtec down to the 4500rpm mark. It just piggybacks the ecu.
I was also under the impression that the honda's actually had 2 profiles on the cam shaft, and when you get to 6000rpm (in my car) it locks the followers to rise on ther higher profile. Saw a good video on how a VTEC works once, can't remember where though.

Zuban · 19 Aug 2006 at 11:36

eidolon said:
I know that Merlin has had this done on his Teg but does anyone know of any Celica owners that have done the same thing.

It appears that Lotus have locked the ECU on the Elise so I don't think that there are any UK owners that have been able to mess with it however Ragnorak Racing offer 230BHP upgrades which include a reflashed ECU over in the US so I don't imagine it will be long before this mod hits our shores.

What are the downsides of lowering the changeover? Surely if it's just an ECU reflash then Lotus would've done this as standard wouldn't they?

Ragnorak also offer a 280BHP upgrade (turbocharged) which lowers the changeover down to 4000rpm, how is it possible to lower it so far? Is it due to the turbocharging?

couple places worth checking out are newcelica.org, make sure you have your crapfilter on though, check out the talk about a piggy back system called camcon. Another good place is the australian toyota owners club, check the sportivo section, a good dig about in there will reveal a few owners running power fc's with the crossover point around 5500 and the power gains are very iimpressive, around 25 lb/ft through the middle. I dont know if either of those systems work with the elise but should give you an idea of the benefits.

Dogbreath · 19 Aug 2006 at 13:36

Oxbow said:
Could you not just replace the ECU with a Toytoa item and fettle with that?. ECUs really are not as scary as people make out. Simple software and a knowledge of electronics can get past most ECU 'Locks' with ease.

Which simple software would this be?

Firestar_3x · 19 Aug 2006 at 15:12

With something as cheap as the Emanage Blue you can shift the factory VTEC point + / - 1000RPM in 100RPM increments, EMB is £169 + Tax and Plug and Play Loom is $189 + Tax & Shipping.

Oxbow · 19 Aug 2006 at 16:11

Dogbreath said:
Which simple software would this be?

Something like ETAS, D-Fuel, Vector....all capable of reading ECU parameters and bypassing locks. If you know ECus you cans usually softmod a chip to bypass any lockdowns in place.

evilowl · 19 Aug 2006 at 17:39

I have a Hondata KPro ECU in my CTR and my vtec point at wide open throttle is 3900rpm with the limiter at 8600. Part throttle VTEC changeover is the same at 5800rpm so I retain fuel efficiency whilst cruising in town or on the motorway.

You lose the kick at cam changeover as it is smoothed out but you gain a lot of power - as standard the CTR is only kicking out 110 odd bhp at 5800rpm, with KPro that figure is around 150 bhp so you get a big boost in midrange power and torque

The daughterboard upgrade in the ECU has a USB port which allows you to connect a laptop and have full mapping (and datalogging) capabilities through the supplied software http://www.hondata.com/kmanager.html

When changing the VTEC point though it's not just as simple as altering the parameter and away you go, you have to alter fuelling and ignition advance across all of the cam rotations from 0 to 50 degrees.

FYI 3000rpm is the lowest VTEC point I have seen in use

merlin · 19 Aug 2006 at 17:56

vtec controllers need mapping with the k20 engine, hence not popular.

lowering vtec on the k20 is normally tailored to take into account induction and exhst changes. crap induction and or exhst and low vtec point is bad for torque.

eidolon · 19 Aug 2006 at 18:50

I've already got the ITG Maxogen air filter and a Quicksilver exhaust so if I can lower the changeover point it might give a decent amount of extra power. I just hope somebody over here managed to crack the ECU and map it to take account of the mods.

Zuban · 20 Aug 2006 at 04:25

eidolon said:
I've already got the ITG Maxogen air filter and a Quicksilver exhaust so if I can lower the changeover point it might give a decent amount of extra power. I just hope somebody over here managed to crack the ECU and map it to take account of the mods.

The one mistake you can make is treating this like a honda engine, although they are 90% similar when it comes to ecu and access to the crossover point they are 100% different on implementation.. it is late and i am drunk

.. I suspect lotus were under some kind of agreement when it cam to the ecu as the power curve is almost identical to the toyota one, despite the fact its ***** . The lotus engineers have admitted there is a lot of room left but can do nothing about it. if you want to go NA tuning you need to take a fresh attitude, and ignore everyone - 260bhp has been done on stock cams with strocker kit to 2.0 litre

or in my opinion go turbo as 8000 rpm + boost is my idea of heaven and the engine is good for it.

olv · 20 Aug 2006 at 11:25

i was under the impression that Lotus set the cam changeover point lower on the Elise as standard?

eidolon · 7 Sep 2006 at 13:56

A guy on SELOC just had his ECU remapped, looks like the torque has been smoothed out quite a bit.

(comparison of standard engine to the one with the reflash)
http://www.dyno-plot.co.uk/dyno/dynoplot/id=336_210&sort=rec&but_sea=qs&sea_simple=toyota/index.htm

Jonnycoupe · 7 Sep 2006 at 15:02

Nice improvement and reinforces the point of not just looking at peak figures. Good increase in midrange grunt there :cool:

MajinV · 7 Sep 2006 at 15:13

eidolon, do you post as philz on SELOC?

Recognised the car in the avatar

NathanE · 7 Sep 2006 at 15:16

Yeah that's him. SELOC'er!

MajinV · 7 Sep 2006 at 15:21

picking up my 111R on Saturday, will post some piccies when i get it home :cool:

Pug · 7 Sep 2006 at 15:49

On the Elise i *believe* they kept the change over on increasing revs the same, but dropped the revert-back RPM to a fair bit lower than Toyota did, this helps avoid on/off power delivery when changing gear.

Celica Club UK .

Personally, not sure i'd want to smooth out the torque curve really, as the surge is fun!

That filter you have - i assume its a panel filter? As Cone filters have been shown to decrease performance due to heat soak...

eidolon · 8 Sep 2006 at 09:15

Jonnycoupe said:
Nice improvement and reinforces the point of not just looking at peak figures. Good increase in midrange grunt there

Yeah, looks like it'll make the car much nicer to drive. Too many people are bothered about having the biggest BHP figure at the cost of low/midrange drivability. I've just emailed Brooke Kensington and it should be released in a few weeks, no ideas on price though so it could be expensive yet.

MajinV said:
eidolon, do you post as philz on SELOC?

Recognised the car in the avatar

Yep, I post at Philz on every other board apart from this one. I guess I might change my nick on here someday just to confuse people

MajinV said:
picking up my 111R on Saturday, will post some piccies when i get it home

Get a decent exhaust as your first mod, 2nd cam is boring with the standard peashooter.

Pug said:
That filter you have - i assume its a panel filter? As Cone filters have been shown to decrease performance due to heat soak...

It's an ITG filter in a carbon airbox and seems to regarded as the best available for the Elise (it wants to be for almost £400!!), reported to give 10BHP but I'll believe that when I see the proof for myself. Sounds great regardless though