Most everyone seems to be maxing out MIVEC advance in the range of 2000 - 4000 rpm. I've been running like this pretty much since I started tuning my Evo. Recently, I've been working on my E85 tune, and I'm now up to 26 psi from about 3000 - 5000 rpm. Out of curiosity, I decided to pull back the MIVEC advance from 28.8 deg to 23 deg in the 2000- 4000 rpm range at high loads. I've only done a couple of runs, but it appears that I gained a solid 10 ft-lbs of torque from 3000 - 4000 rpm. I need to do more runs to confirm, but I'm wondering now if there may be some reason that less advance MIVEC would be better at higher boost values.

 

Exhaust gas blow-back reducing the inlet charge quantity and buggering the inlet charge quality?

 

Hmmmm this might explain my relative loss of torque after switch to e85 as well. I mean proportionally I gained way more HP than torque. X Torque and X2 HP approx.

I was getting peak torque about 500 rpm sooner as well. What happened to your HP value when you noted gain in torque? Same,less or more?

TIA

 

interesting. I will like to see where this goes.

 

In my newer MIVEC tables I taper the advance back out past like 220 load or so since its primarily a spool tool. It seems that you can leave it and the boost stays high it just doesnt feel like its going anywhere, so thats why we started tapering it back out.

 

John what do you taper to? I would think you would still leave some advance.

 

sounds like you're tapering mivec before you reach peak boost. After peak boost do you continue to taper it down to zero or reintroduce advance as boost starts to taper to redline?

 

What I would guess is that at higher boost on small turbo (rising backpressure with rpm), less scaveining might start to outweigh the negative effects of a shorter compression stroke (due to intake valves closing later).

Also, too much of a good thing (scavaging when boost pressure is higher than turbine pressure) will start to pump potential HP (air/fuel) out the tailpipe.

Unfortunately for me my car is equipped with fixed cams (and a worse turbo for backpressure) so I couldn't benefit from any of the negative affects of MIVEX if I tried.

 

Don't you have data on back pressure vs rpm and boost pressure for the stock turbo?

 

 

Found the post. Was kinda hard to find.

https://www.evolutionm.net/forums/sh...d.php?t=327719

This suggests that under high air flow conditions (higher boost levels and rpms), exhaust gas will blow back into the intake when there is significant cam overlap. Exactly what merlin.oz said. :-) Time to tinker further with the MIVEC values.

 

high air flow or high pressure?

 

^^is that mivec map JohnBradley posted on e-85 or pump?

 

High airflow, but of course boost increases airflow.

According to the table header its for E98 with a Green turbo.

 

That is an unchanged S2 map from the days on straight pump and 30 psi, E30 and 30 psi, and now E85 or E98 and 30psi. That particular scaling approach fits the needs of both the Green, the 4" FMIC, and high boost and revs pretty well independent of fuel.