03whitegsr

iTrader: (8)

Along with what Aaron said, there is kind of a threshold where going too rich costs you A LOT of power. On a 2G DSM on a mustang dyno, 10.8 to 11.3 I saw about 25 WHP at the 450 HP level. 11.3 all the way to 12.5 did very little for power.
Because there was minimal changes in power with the AFR, I left the car around 11.3:1 then turned to timing advance. The car would consistently pick up about 6-8 WHP per degree until it would hit a point where an extra degree only added about 1-2 hp. Next degree did nothing for power but the knock sensor also didn't show any other signs of trouble. Pull out 2 degrees from there and called it done. Car always ran great on that tune, even when the boost got turned up a little extra. That extra 2 degrees pulled out from peak allowable timing seemed to give a nice little safety margin without costing any real power.

These are just on a particular setup. I've seen very different results on other setups. A suby for example I tuned picked up 80 WHP from 600 WHP with 2 degrees of timing. Next degree did nothing for power and started to show signs of unstable combustion. This was on VP import. Not sure if it was the setup or the fuel that gave it that razor sharp "edge" the tune had to sit on.

On the stock turbo on 91 octane, to push the turbo hard on 91 octane, I've had to run richer then desired and fairly low timing advance. The car did consistently pick up power with each PSI though. At the point where the turbo was getting maxed though, it was getting pretty slim on the gains with mostly just picking up torque.

JohnBradley

iTrader: (30)

MIVEC heads have different coolant passages around the combustion chamber, though I can tell you everything to the left side of #1 is the same between the 2. The 03-04 heads have far more problems with core shift and occluded bowls and early exit/entry out of the runners. I made a thread awhile back called "cylinder head tech" that had pictures and the whole bit.

The MIVEC heads have casting "bumps" on the intake side, where the VIII has them on the exhaust further compounding the restrictions. OE chamber size is around 47cc (listed by Wiseco) but I swear I saw somebody post it was actually more like 45.5cc on average. I dont bother to cc combustion chambers normally so I cant say.

I think in addition to how the cylinder head is actually different, the issue of inconsistency in casting leads to an inconsistent MBT measurement. Like I said the best I have ever seen an VIII head was 21* (the whole crazy stock cam thing aside) but on average they are 19-20*. I have seen one race motor that made peak hp at 16* and was perfectly happy that way. I know that there are some heads out there that have been worked far in excess (price tag to match) to what we normally do that can run to MBT on pumpgas.

aaron

tscompusa2

iTrader: (22)

Is there any logical explanation why mitsubishi gave the 1g's so much of an aggressive timing curve? I remember when I tuned my first 1g coming from a 2g I was so confused inside dsmlink with the timing sliders.. turned out i had to pull a crap ton of timing because the stock map was so aggressive, 20*+ in areas vs adding it on a 2g.

How comes mitsubishi gave the 1g that much timing? this was a 92 6 bolt

03whitegsr

iTrader: (8)

Lower compression.

The 1G may have also been originally tuned for higher minimum octane fuel too?

wizzo 8

iTrader: (35)

subcribed

JohnBradley

iTrader: (30)

7.8:1 compression and cams that didnt make power past 6200 (24* there in the stock map) anyway. Nothing about 1Gs really compares to be honest. They ran 12psi of boost, lower compression, bigger intake ports, bigger combustion chamber (farther distance for the flame front), small cams, dink turbo.

The 2G did have a smaller turbo to be fair, but it was higher compression and had a head that was very similar to the Evo 8 in comparison to the 1G. What we have found is that as they get more compression, bigger cams, and a bigger turbo they really end up all about the same.

aaron

JohnBradley

iTrader: (30)

Here is the thread. It only has pix of the VIII head, I will have to look and see if I have any of the head porting we did on my personal cylinder head.

https://www.evolutionm.net/forums/ev...head-tech.html

LGshow19

iTrader: (51)

Subscribed... great info

ace33joe

iTrader: (2)

Great info!

I guess I have to play with boost, timing, and AFR again.

Currently running ~21 psi, 11.7 AFR, 13* @ 7krpm (stock 10.5 hotside turbo, stock cam, 100 RON octane fuel), but I guess I should try richer AFR + higher timing see if it makes more power using VDR.

Please share some experience who has similar setup.

Thanks!

Force 6

all depends on setup

JohnBradley

iTrader: (30)

That sounds about right actually. I'd run a spike and make more low end and mid range, but the power out the top will remain the same generally.

ace33joe

iTrader: (2)

Thanks for the advice!

I am using ~23 psi near mid range, and tapering down to ~21 psi near 7krpm.

I used to run less boost up top, but after Amsoil air filter (open element), I hit 21 psi with less solenoid duty cycle. (Less vacuum from the intake helps more than I thought. )

AFR is about 11.3, timing is 2* at peak torque. I tried more timing, but I get non-zero knock sum, so I left it at 2*.

tscompusa2

iTrader: (22)

sounds like you got a solid and safe tune on your car. did you confirm it didnt gain more torque after 2* ?

also what filter before the amsoil filter? id love to see the perrin foam filter vs the amsoil filter since they are so different.

ace33joe

iTrader: (2)

Thanks for your comment.

I guess I am octane limited near peak torque, so I don't think I can use more timing although it might make more torque. I do not have access to higher octane fuel than 100 RON, so I guess only thing I can do is to make it richer and add 1* more and see if it makes more torque. (Unless I do more hardware upgrades like better flowing cylinder head as Aaron said. )

I used to have stock air filter housing along with a HKS hybrid panel filter. So the baro reading @ MAF housing change is more dramatic than using some other open-element filter.

According to another great thread "Air filter shootout", Perrin seems to perform very good, but I just personally prefer a dry air filter element, so I went with Amsoil.

Check out the "air filter shootout" thread if you haven't seen it yet.

nightwalker

Just a side note: I tested the Buschur/Vibrant filter against my Perrin and the Buschur held better boost up top. The baro was slightly better on the Buschur as well.