Hi guys,

I've had my MS2v3.0 running good for about a year now.
I cracked an iron about 2 months ago and finally have my new engine back together with some upgrades.
It is a stock port big iron S5 TII block with 9.7:1 NA rotors.
Garrett GT4088R turbo with water-to-air intercooler
Bosch 1150cc EV14 primary injectors
Bosch 1600cc EV1 secondaries
Walbro 400 / Aeromotive FPR at ~45psi base.
AEM water meth currently approx 500cc/min

My tune is still fairly rough under boost. Still in the 10s most places.
I’m getting a bit paranoid at how low all the VE values are in the high boost/RPMs compared to my old tune with a different turbo and stock primary injectors.
For the most part, my VE table only goes from 30-60, my old VE map was much approx 20-160.
I changed the primary injector value and that is pretty much it.

Having this very small VE range makes running low load difficult. Changing one cell in my idle are by a value of 1 can make my idle AFR go from mid-11s to hunting off the charts.
Also, having a VE of 50 at 6000rpm and 13psi seems really weird, although it seems to not mind it.

Any advice would be greatly appreciated.
Please see attached MSL, MSQ, and VE screenshot.

Thanks

 

I've uploaded an old map before I changed injectors and retuned. The VE map is drastically different and much more linear.

 

did you change your req fuel if you dont thats normal.also the right inj deadtime play a big role in the calculation.

 

I did not change the req fuel. I thought one of the advamtages of having an accurate required fuel value is so the injectors can be changed and the VE doesnt have to be rescaled.

I'm using the recommended dead times from the manufacturer.

 

The Req'd Fuel is based ideal 100% VE at stoich with the set of injectors you input. So if you change the injectors, it changes the Req'd Fuel and thus the VE values in the table are applied to incorrect injector size assumption, so wrong amount of fuel, meaning you need to adjust the VE table to compensate.

The end result are radically high or low VE values, and lost resolution.

With your 1100CC primaries, your Req'd fuel will be much lower. 1100CC primaries is also 2x stock, which themselves idle the car around 1.7mS. So you'll be less than 1mS injector time, which is very into the injectors non-linear area as well as the limitation of how short it can open for.

In general, I have moved to SMALLER primaries and larger secondaries. For example my Cosmo runs (will run)RX-8 450CC primaries. Frankly I might change that to the 360CC versions. This gives far better fuel control at light loads because it is much easier to add duty cycle, but far harder to remove duty cycle below about 1.5mS.

Of course my big old dirty bridgeport runs 720CC primaries and idles at almost 3mS, around 14:1.

 

Thanks, Aaron.

I am still a bit confused by "Required fuel" value.
When I had the 550cc stock injectors, I was using a required fuel of 10.0 (5ms) per your website.
Do I simply change that to 5.0 (2.5ms) if I double the primary injector size?
Does the secondary size impact anything?

If I use the required fuel calculator with 550cc injectors, 1300cc, 2cyl, and 14.7 stoich, I get 7.9 (3.95ms)
If I use 1100cc injectors, 1300cc, 2cyl, and 14.7 stoich, I get 4.0 (2.0ms)

Should I use 5(2.5ms) or 4(2ms) or does it not really matter since I'll be retuning everything anyways?

Thanks

 

You can use the Required Fuel calculator to find the ballpark value but yes, I suspect it will end up around 5. The Req'd fuel calculator takes into account the primary injector size only since those are the injectors feeding the engine in all circumstances. Secondaries are only brought in when needed.

When you recalculate it with the new injector size it will drop the Req'd Fuel value. Now you must rescale your VE table if you want to maintain your tune.

I'd confirm with Ken that the calculator wants to see 1300CC and not 2600CC it used to be 2600CC.

I'm almost certain it's 1300CC though. Just downloaded the latest firmware and checked. I get a Required Fuel of 4/4 when using the calculator at 2 rotors/1300cc/1100cc, everything else default. Looks right to me.

I would be remised to not point out that the manual does say the Req'd Fuel is calculated using primary injectors only.

And remember, after changing the value your VE table is now wrong. Highlight the table and multiply it by 2.5, which should put you in the ballpark. Now CAREFULLY approach boost and SLOWLY confirm you are good to go.

 

Thanks, Aaron.

Hopefully when I change my required fuel value, the engine will run on my old 550cc tune and get it driving well enough to use VE Analyzer. Obviously caution will taken once I start tuning in boost. I'll know pretty quickly of its off significantly.