MIVEC kick-in = Loss of power

spetz · Post by **spetz** » Thu Dec 23, 2004 5:15 am

When MIVEC kicks in it seems like the is a slight loss of power for a few hundred rpm until power climbs back up again.
What can this be? I have a fuel cut defender and played with that and the power loss seems to have gone down considerably. Also the car smells like petrol heaps when air con is on and it might be running rich.

Post by **smorison** » Thu Dec 23, 2004 7:14 am

there is a loss of power when the ECU activates the high speed cams... the unique mods we've built have gotten rid of substantial amounts of this... unfortunately due to the nature of what's happening in the engine i don't believe this can every be fully eliminated.

Boris · Post by **Boris** » Thu Dec 23, 2004 8:27 am

I don't know about the car running rich, only when the aircon is on. That seems a bit impossible

donno...

My car run slightly rich all the time.

Maybe you should take it down to Jakes Performance, and get a tune.

Also, the gearbox is designed so that if you shift at 8k, you will avoid this small dead zone, so in theory you only hit it once at the start in 1st if your racing.

mrStumpy · Post by **mrStumpy** » Thu Dec 23, 2004 10:56 am

I have a mivec controller. And when I change mivec kick inn point, it seems to accellerate slower. I read previous in this forum a tread discussing the possible benefits (if any) in having a MC, and I cant really see the point.... except... everytime I disconnect my battery and the ECU resets itself, the car only runs on 4 cylinders until I change it in the mivec controller.

I guess it would be good hiving it when I turbocharge my gpx

RichardH · Post by **RichardH** » Thu Dec 23, 2004 3:26 pm

I was talking about this just this morning with an EFI specialist.

He reckons it's very common for manufacturers to build in a bit of rich running at (a) critical "cutover" points for things like high-lift cams, and (b) very high rpm.

This is a safety margin, to protect against damage through detonation occurring. Those points are apparently the most likely places for preignition to occur.

The ARF graph from my last dyno run very clearly shows a rich spot at around 5700, and again over 7500. So there you go.

He also reckoned, being a conservative type, to leave it well alone, as it's A Good Thing to have a safety buffer.

- Rich

spetz · Post by **spetz** » Thu Dec 23, 2004 6:22 pm

So everyone experiences this loss of power, and it isn't just me?
How come VTEC YO!!!!! then, gives you a kick?

Also I have been in a car of a member here who had HKS filter, HKS exhaust and tuned unichip and he got a bit of a power increase kick once MIVEC kicked in (nowhere as drastic as VTEC YO!!!!! but still a little kick)

And yes I noticed if I changed at very high rpm I never get into below the 5600 rpm or so where MIVEC kicks in

G_A_V · Post by **G_A_V** » Fri Dec 24, 2004 2:06 am

The whole point of having a v6 is spreading the power out more evenly, which is why you dont get the kick like vtechs. Also the fto's cams are proberbly not as aggresive, but with any varible valve timing system, there is going to be some loss of power during the switch

Post by **smorison** » Fri Dec 24, 2004 8:33 am

the "kick" is due to the CAM changeover from low to highspeed CAM being no where near as smooth and refined as that in the FTO...

spetz · Post by **spetz** » Fri Dec 24, 2004 11:04 am

G A V -
But VTEC YO!!!!!'s don't have power loss? And I been in a celica VVT-Li and that gave a bit of a kick.

Back the question, do all FTO's have power loss? I though it's smooth and power just keeps climbing with no loss or kick as such

Post by **smorison** » Fri Dec 24, 2004 11:53 am

spetz wrote:G A V -
But VTEC YO!!!!!'s don't have power loss? And I been in a celica VVT-Li and that gave a bit of a kick.

Back the question, do all FTO's have power loss? I though it's smooth and power just keeps climbing with no loss or kick as such

is that based on dyno run ... or back of the seat sensation?

spetz · Post by **spetz** » Fri Dec 24, 2004 8:01 pm

This is back of the seat sensation.
But obviously a kick of extra power must be better than a kick of less power, even if it's only back of a seat sensation.

Anyway, like I said I played with the fuel cut defender on the car and the loss of power has nearly all but went away. The fuel cut defender connects to the MAP sensor, which I assume just raises/lowers the voltage reading to the ecu about the vacuum the engine runs? I set the fuel cut defender it as little as possible, which I hope is the stage where the FCD doesn't do anything.

Any reason of why this was fitted to the engine?

mrx · Post by **mrx** » Sat Dec 25, 2004 7:30 am

It is true that without a spike in the power range, it does remove a bit of the sensation of acceleration. However, it does mean that the engine is giving a smooth power delivery across the range = better flexibility.

I do not have the drop off in the power like you get on other cars, and as far as I know the ecu, fuel system etc are all stock. And that is not just a sensation in the car, it is confirmed on the dyno.

But if you really want a kick - get a turbo!

spetz · Post by **spetz** » Sat Dec 25, 2004 10:02 pm

The whole point of the V6 was to stay N/A

Turbo is getting old to be honest, sure it's ultra quick, but there's nothing amazing seeing a quick turbo car...
Now a quick N/A small capacity car... now that's something...
Besides I wanna be quicker than turbo's (obviously not all but something like 200's, rexes etc)

Anyway the car is going into the workshop next year (end of feb or so) I'll get everything checked/fixed and let you guys know

mrx · Post by **mrx** » Sun Dec 26, 2004 6:51 am

spetz wrote:The whole point of the V6 was to stay N/A

Turbo is getting old to be honest, sure it's ultra quick, but there's nothing amazing seeing a quick turbo car...
Now a quick N/A small capacity car... now that's something...

Totally agree - that is the whole point too it. Turbo is the easy way of making good power from small engine, so to stay NA and still turn out good numbers is fantastic. And too me, the FTO has one of the best sounding engines on the road, which is one of the most appealing things.

Of course, the problem then is to gain small amounts of power you have to spend big dollars.

spetz · Post by **spetz** » Sun Dec 26, 2004 8:03 am

How do FTO's sound with a muffler?
My induction sound is beautiful but I am running a baffled muffler so I can't hear anything from the end side.
Just wondering if I should put a muffler?
It has a 2.5" mandrel exhaust with stock extractors

D-TRAIN · Post by **D-TRAIN** » Sun Dec 26, 2004 7:17 pm

spetz wrote:The whole point of the V6 was to stay N/A

Turbo is getting old to be honest, sure it's ultra quick, but there's nothing amazing seeing a quick turbo car...
Now a quick N/A small capacity car... now that's something...

Just bear in mind though some turbo engines are small in capacity as well. Prime example is the 4g63, and it's potential for power is amazing.

If you get the chance, check out the FQ Evos. You'll be surprised what a 2L turbo engine can do.

spetz · Post by **spetz** » Mon Dec 27, 2004 10:25 pm

Yes I seen the new FQ 400
Even still I know you can get nearly double that power from a 4G63 pretty easily.

But I wasn't talking about beating the quickest turbo cars out there.
But I am from ACT and I noticed most turbo cars here are left stock (maybe filter and exhaust) and I am just aiming to be quicker than them.
Or quicker than most Holden/Ford V8's (with the exception of the top of the range HSV and FPV cars)

Boris · Post by **Boris** » Thu Dec 30, 2004 6:19 pm

Though i should add this: If you want some form of a "kick" or a "push" you will only feel it in the mivec zone. I have an excellent CAI system, Blitz Filter, and extractors, no cat, and cannon exhaust. That will give you a slight push in the seats

Also because i have a Mivec controller i can move the Mivec point further up the rev range, i have it on 5.8k... if you have it at about 6.2 you really feel the change in power, which gives you that push. but performace wise i haven't noticed much difference in having it at 5.8k or 6.2k or what ever...

spetz · Post by **spetz** » Sat Jan 01, 2005 2:28 am

That's a bit high for the MIVEC to kick in though isn't it?

It would make you a bit slower anyway, because the only reason it gives you a kick is because had it already been in the MIVEC range there would be more power at 6100 rpm therefore eliminating the push.

What extractors do you have?

Also, HRD2BQT, what's going on with that twin turbo conversion you were telling me about? Can you chat to charlie about the 2.5 litre swap. I'm not in Oz at the moment but when I get back (mid february) I'll be coming to sydney again