[Chrome383Z]

Quick question, I picked up a 103mm Snout for my 2650. STD kit comes with the 87mm which is what I have now. Currently running a 95mm TB with 95mm/87mm adapter. I have a 95mm/103mm adapter that I used with my N/A setup and MSD intake.

Do you think I would need the tune touched by adding the Magnuson 103mm Snout, adding the 95/103 adapter and keeping the 95mm TB and STD rotofab?

It would definitely be interesting to see the results of only that change, but i'm not willing to pay for a tune for only that. I'll add a 103/Big Gulp if I have to retune, but that will have to wait till next year as I'm capped out on car spending this year. LOL Wife rules.

[laynlo15]

I would open up the holes on the 95mm TB to match the 87 pattern and get rid of the adapter. Use a Dremel as I did so I could run the 95mm on a 87mm bolt pattern as the 103 snout has. You could try it but someday you may need a slight Maf change but I doubt it would be a huge change.

[Joshinator99]

Originally Posted by Chrome383Z

Quick question, I picked up a 103mm Snout for my 2650. STD kit comes with the 87mm which is what I have now. Currently running a 95mm TB with 95mm/87mm adapter. I have a 95mm/103mm adapter that I used with my N/A setup and MSD intake.

Do you think I would need the tune touched by adding the Magnuson 103mm Snout, adding the 95/103 adapter and keeping the 95mm TB and STD rotofab?

It would definitely be interesting to see the results of only that change, but i'm not willing to pay for a tune for only that. I'll add a 103/Big Gulp if I have to retune, but that will have to wait till next year as I'm capped out on car spending this year. LOL Wife rules.

You’re fine. Won’t be a huge difference since you’re still on the same TB and CAI. Just datalog it and make sure things aren’t out of whack. You have a wideband and HP Tuners, right?

[Chrome383Z]

Originally Posted by Joshinator99

You’re fine. Won’t be a huge difference since you’re still on the same TB and CAI. Just datalog it and make sure things aren’t out of whack. You have a wideband and HP Tuners, right?

Yeah that’s what I’m thinking as well. I’ll do a few pulls and watch it…. Running E65 so should have some bandwidth if it gets a little lean.

[Joshinator99]

Originally Posted by Chrome383Z

Yeah that’s what I’m thinking as well. I’ll do a few pulls and watch it…. Running E65 so should have some bandwidth if it gets a little lean.

[cjperformance]

Tuning the MAF is super easy once you get used to it. I highly recommed everyone at least know how to do a datalog and rescale a MAF.

Its probably the most common thing to need touching after practically any mod, so being able to do it yourself for free is better than paying hundreds of dollars for someone else to do it every time you do a mod.

Goatrope Garage on Youtube has some good starter vids on this. Im sure we can help too if you post up some logs and want to learn.

[radz28]

I started with the 87mm snout and a LT5 TB (ported the snout and TB and re-drilled the TB). I tuned the MAF for that stuff, mostly for the BG. No biggie. I switched to a 103 snout/103 Soler and didn't really have to make too many changes to the MAF, but I did see the need to. I did not change scalers for the TBs either. Although - I've messed with VTT/VVE/DD from the start, and I think that's why I didn't have to.

I agree that it's a good idea to tip your toes into the pool on MAF rescaling. It's pretty easy and there are lots of good videos on it. Just make sure you set yourself up with what you need to do it right, and it will be just fine.

[Chrome383Z]

Complete noob on tuning (mechanical ENG not electrical/controls lol) but do I need to rescale the MAF if I keep the STD rotofab? Let’s say I kept the STD rotofab and changed the snout and added a 103mm TB. Obviously the car is going to get more air, and would need more fuel, but I would think the MAF would still read as normal. I’m more familiar with Gen III cars and IIRC at WOT they went into PE which ignores the MAF and puts in a fixed amount of fuel. So I would think I would need to add more fuel in this scenario right? “Rescale MAF” I would think would need to be done if the diameter of the inlet tube changes (aka Big Gulp) or am I wrong?

[KingLT1]

Originally Posted by Chrome383Z

Complete noob on tuning (mechanical ENG not electrical/controls lol) but do I need to rescale the MAF if I keep the STD rotofab? Let’s say I kept the STD rotofab and changed the snout and added a 103mm TB. Obviously the car is going to get more air, and would need more fuel, but I would think the MAF would still read as normal. I’m more familiar with Gen III cars and IIRC at WOT they went into PE which ignores the MAF and puts in a fixed amount of fuel. So I would think I would need to add more fuel in this scenario right? “Rescale MAF” I would think would need to be done if the diameter of the inlet tube changes (aka Big Gulp) or am I wrong?

No GM ECU that I recall ever ignored the maf signal for fueling in PE mode if dynamic airflow is disabled above set point. GM almost always disables dynamic airflow above 4k rpm and relies on MAF for final fueling. If the MAF is disabled then ECU relies on VE/VVE table for fueling. If the MAF curve is correct, then the AFR will hit the PE target.

That being said the 103 should not require rescaling the MAF, but you will likely need to adjust the virtual torque tables so the engine doesn't idle with negative timing.

[Chrome383Z]

Originally Posted by KingLT1

No GM ECU that I recall ever ignored the maf signal for fueling in PE mode if dynamic airflow is disabled above set point. GM almost always disables dynamic airflow above 4k rpm and relies on MAF for final fueling. If the MAF is disabled then ECU relies on VE/VVE table for fueling. If the MAF curve is correct, then the AFR will hit the PE target.

That being said the 103 should not require rescaling the MAF, but you will likely need to adjust the virtual torque tables so the engine doesn't idle with negative timing.

I’m just changing the snout right now, not the TB. I didn’t know that I thought they all went into Speed Density mode when at WOT. Maybe that was 3rd Gens, lol. This is why I haven’t messed with trying to tune myself, but I am quick to learn and this is such a minor change that it would be a good learning experience.

Im thinking I’ll do a pull this weekend, throw the new snout on and do a short pull maybe 4k and post results. I’d love to learn how to do simple modifications in the tune.

[KingLT1]

Originally Posted by Chrome383Z

I’m just changing the snout right now, not the TB. I didn’t know that I thought they all went into Speed Density mode when at WOT. Maybe that was 3rd Gens, lol. This is why I haven’t messed with trying to tune myself, but I am quick to learn and this is such a minor change that it would be a good learning experience.

Im thinking I’ll do a pull this weekend, throw the new snout on and do a short pull maybe 4k and post results. I’d love to learn how to do simple modifications in the tune.

Gen 3,4, and 5 all go into open loop PE mode under WOT conditions. The MAF is still in play for final say in fuel control. However it is still a preset...so whatever frequency range the ECU sees from the maf is the amount of fuel it will add. They do not use o2 sensor or fuel trim data for fuel correction in open loop. Some of the newer cars like the C8 now have wideband o2 sensors which allows the ECU to self-correct fueling in both open and closed loop.

Sounds like a plan! It's always best to learn how to do this stuff yourself. Get a base tune and start comparing changes. Make small simple changes on your own, verify results...rinse repeat. That is how I have learned over the last 10 years.

It's pretty easy to adjust the maf curve once you have an afr error histogram setup in your VCM scanner. This will show you how much variance is in your AFR at any given point in the maf frequency range. Then all you do is take the error percentage and add or subtract it. I usually only do half of the difference. So for example, if the AFR error is showing 3% lean from 9000 to 10000hz, I simply multiple those lean frequency cells in the maf curve by 1.015, then go make another log. Once you are +/-2% then I use .005 or .995 depending if multiplying(adding) or dividing(subtracting fuel). Once the maf curve is right the AFR should hit what you are commanding in the PE table. Now you can adjust the PE table to change fueling.

[JANNETTYRACING]

Originally Posted by Chrome383Z

Quick question, I picked up a 103mm Snout for my 2650. STD kit comes with the 87mm which is what I have now. Currently running a 95mm TB with 95mm/87mm adapter. I have a 95mm/103mm adapter that I used with my N/A setup and MSD intake.

Do you think I would need the tune touched by adding the Magnuson 103mm Snout, adding the 95/103 adapter and keeping the 95mm TB and STD rotofab?

It would definitely be interesting to see the results of only that change, but i'm not willing to pay for a tune for only that. I'll add a 103/Big Gulp if I have to retune, but that will have to wait till next year as I'm capped out on car spending this year. LOL Wife rules.

Installing a 95mm on a 103 snout creates a step on the back side of the TB.

The Step creates a turbulence at the supercharger entry.

I can't say it will, Because I never did this, but can say it might cause some Idle and tip in issues we have seen on other platforms, Like when guys were installing 90mm TB on Fast 103 manifolds.

We actually offered a 90mm Ring to press in the 103mm manifold behind the TB to make the Transition smooth.

All the Whipple come with a tapered reducer for the Throttle body to supercharger inlet.

The change of the snout only, would not effect the calibration providing it is spot on to begin with.

Ted.