[AWD Addict]

My car is scheduled for service next month, and I'm debating whether to upgrade my 5.5" IC to a larger unit. I'm MHD stage2+ FBO, and after some 93 octane datalogs, my IATs were on the high side, and I was experiencing timing pulls across all cylinders. On the same tank, tuning down to 91 octane got rid of all anomalies.

While this could have been a suboptimal tank of gas (It was Sunoco, for whatever that's worth), I think addressing the high IATs is the right next move for me. I'll note I'll likely add one-step cooler plugs, but I'm not expecting anything more than a few degrees IAT improvement from those at best.

I'm having trouble finding any good data I can put together on comparing IATs between a 5.5" stepped and a 7.5" IC. Is my only option to comb through the "look at my log" threads, and catalogue who has what tune and IC, and tehn find the comparable one with a larger or smaller unit to compare to? For me that'd be pretty crappy science, given all the atmospheric and other variables.

How can I find out what IAT improvement I can reasonably expect from upgrading to the larger cooler?

Thanks!

[NoGuru]

I had an ETS 5" for a while but after full bolt on's IAT's started to get high and after turbos and fuel upgrades I had to go to a 7". Now on pulls my IATS go down.

[AWD Addict]

Any before/after IATs from comparable seasons/ambiant temps?

Sounds like that's what I'm going to have to do.

[AmuroRay]

Depth doesn't matter as much as frontal area. Always go with a stepped unit - VRSF Race is my vote, I use one on my FBO M235i

[AWD Addict]

My 5.5" stepped has decent surface area, but I think it was before they increased the fin density. Not sure how much that impacts things, but it's certainly not helping.

Great unit otherwise, and as long as I keep the tune dialed down to 91octane.

[AmuroRay]

Originally Posted by AWD Addict

My 5.5" stepped has decent surface area, but I think it was before they increased the fin density. Not sure how much that impacts things, but it's certainly not helping.

Great unit otherwise, and as long as I keep the tune dialed down to 91octane.

Fin density is surface area, and it matters a LOT, as much as frontal area. My Race Intercooler is 18 fins/inch. A good core should be at least 16

[AmuroRay]

https://datazap.me/u/amuroray/rk-fro...28-29-30-31-32

Log - 3F over ambient

[SlowE92]

Originally Posted by AmuroRay

Depth doesn't matter as much as frontal area. Always go with a stepped unit - VRSF Race is my vote, I use one on my FBO M235i

You don't notice any noticeable lag running the Race intercooler on stock turbos?

[AmuroRay]

Originally Posted by SlowE92

You don't notice any noticeable lag running the Race intercooler on stock turbos?

Zero lag. Lag from a bigger Intercooler is a myth on this platform.

[oVeRdOsE.]

Originally Posted by AmuroRay

Zero lag. Lag from a bigger Intercooler is a myth on this platform.

because the piping remain the same size +/-, bmw IC is well thought. I found out the piping size has a bigger influence on lag than the bigger intercooler system total volume.


Audi are known to have stupid piping route with massive knotch bottle neck. Bernoulli state smaller area = higher speed at constant flow. So when people put full size IC, they fell a ''butt-dyno lag''.

I agree, on a TT setup I really doubt people will feel any difference.

I still have my 5'' vsrf on my ST setup, Ill log temp, but ill run a conservative tune , with a medium size turbo (6262)

[Torgus]

Originally Posted by AmuroRay

Zero lag. Lag from a bigger Intercooler is a myth on this platform.

This. Boost builds so fast on twins or a single, well not fast on a single but you know what I mean, the only lag is 100% a placebo effect because you read what someone else wrote online. Air space fills up VERY fast with pressurized air from the turbo, or head restrictions however you want to look at it. Lag is non existent.

Get the biggest IC you can fit. Buy once, cry once and be done with it. In this case it would be the BMS/VRSF 7.5'' 'race' stepped IC. I know others make a similar sized IC and it could just be a knock off. BMS VRSF have had excellent customer service the few times I have had to contact them. An IC is like a big heatsink. This is part of how the race IC works, and why it weighs so much. You want the largest you can get with the most frontal area. Depth helps but frontal face area is most important.

I would vote the 7.5 stepped race every day of the week. Add on a small shot of meth in the CP for good measure. Car will be VERY consistent regardless of the outside temperature. With good coils and plugs you should not have many timing pulls unless your tune is set to aggressively for your octane.

What service are you having done? Just spark plugs? Do them yourself, super quick and easy to do. I probably have a spare socket you can have if you don't have the thin walled one you need.

GO Bs!

Edit: You never hear anyone say I should have gone with a smaller IC.

[AWD Addict]

I've got a bunch of other service things to solve for, so I won't be doing anything. I don't really turn wrenches in the driveway anymore, so anything else is happening with my indy shop.

I've got something going on with my transfer case, I need to swap my winter wheel/tire package on, and I think I'm going 1 step colder plugs. I might just punt and see if I can cheat a few degrees of IATs with the 1 step colder plugs before doing anything else.

Candidly, I'm kind of annoyed the IC I bought is obsolete, because they didn't have high enough fin density. In any other field, a superseding part that corrected a deficiency would be offered up to customers with the older part as a core trade in. I agree on the 7.5" though. If my IATs next summer are still keeping me from running 93 octane maps without timing issues, I'll be going 7.5" all day. When I did the 5.5", I wasn't sure I'd end up FBO, and generally people all said it would still be enough for that, but without cutting. So it made sense to me. C'est la vie.

[Torgus]

Originally Posted by AWD Addict

I've got a bunch of other service things to solve for, so I won't be doing anything. I don't really turn wrenches in the driveway anymore, so anything else is happening with my indy shop.

I've got something going on with my transfer case, I need to swap my winter wheel/tire package on, and I think I'm going 1 step colder plugs. I might just punt and see if I can cheat a few degrees of IATs with the 1 step colder plugs before doing anything else.

Candidly, I'm kind of annoyed the IC I bought is obsolete, because they didn't have high enough fin density. In any other field, a superseding part that corrected a deficiency would be offered up to customers with the older part as a core trade in. I agree on the 7.5" though. If my IATs next summer are still keeping me from running 93 octane maps without timing issues, I'll be going 7.5" all day. When I did the 5.5", I wasn't sure I'd end up FBO, and generally people all said it would still be enough for that, but without cutting. So it made sense to me. C'est la vie.

You could always add meth or run some E85 or both. Both will help with in cylinder cooling and less timing pulls. BUT then you will want to crank up the boost more

[BMWdmk]

Switching to 7.5" from 5" I'm seeing 10-15 degrees above ambient freeway cruising
5" I was running same conditions 15-25+ degrees above ambient again freeway

During a pull my 7.5 drops IATs by a degree. My 5" climbed up to 5 degrees

Only variable here is the 7.5" intercooler came with three inch piping on the cool side up to my 3" chargepipe. Slight smaller hardware came with my 5" cooler

Happy boost season!