[XutvJet]

I've owned my M235 for nearly 2.5 years and this is my second turbo car. Prior to my M235, I had a 2012 WRX with a Stage 1 tune. Living in Kansas City, I get to experience all seasons and temps. We can get sub zero in the winter and 105+ in summer. In the 40-70 degree range, my M235 feels very strong and is what you'd expect for a turbo in cooler, dense air. However, when ambient temps rise above 80 and the humidity is up, I have to say this car is more affected by the heat than most any car I've owned in the past. It still faster and quicker than any of my prior cars, but the difference in power delivery and drivability in the hot is rather surprising once the motor is heat soaked and the air intake temps (IATs) are up.

I know late model turbo cars will create more boost to compensate for the poor density altitude summer conditions in an attempt to maintain rated power and commanded torque, but the increased lag and reduced power low to midrange power is certainly felt. If you're sitting a light or had the car parked for a while (i.e., high IATs; above 120+ degrees), the power can be quite neutered. If you get on the car hard, the motor sounds strained and far less eager to rev happily.

Perhaps it's an N55 thing because I've read numerous articles of the M2 where journalists note just how much difference there is in power between a cool day track run and a hot day track run. On dynos, you can a see power above 5000rpms really getting reduced when the M2 and M235 N55 motors are heat soaked. From what I've seen, it a difference of around 30whp/wtq above 5000rpms.

Using my Torque app, the IATs can get staggeringly high when sitting at lights and parked for a while (130+ degrees), but the car does a decent job of clearing out the hot air once you're driving at speed for a minute or two. Even then though, when IATs are above around 110 degrees, there's clearly some timing getting pulled and power is down.

I do run 93 octane exclusively. I know many will chime in and say get an upgraded intercooler, but that's really not the issue here as this is an off-boost heat management matter. The IC upgrades are great for extended hard driving but won't do anything for low speed, around the town driving as there is minimal air moving through the induction system. If anything, the all metal construction of an aftermarket IC could actually make heat soak worse in these conditions.

For those with M240s and the B58 motor, do you notice a decent power drop in the summer?

[Maynard]

Doesn't the M4 have a water-mist sprayer to help cool the IC - that shouldn't be too hard to rig up, at least for a quick trial to see if it helps.

[ianp622]

I live in FL with the M240i and I never noticed any difference in summer vs. winter.

[B58togo]

It’s bad with the B58 too. Car drops a tenth with each run at the track. Start around 12.30’s and once I slow down to the 13’s, I get frustrated and leave. At least the N55 has intercooler options!

[morphomeman]

The real problem here is the laws of physics. We're working on fixing them.

[vietboyx1115]

Living in Dallas, there's a noticeable difference when the days are 95+ degrees and the nights are in the mid-70s. I know you think that an IC upgrade won't do much at slow speeds, but I recently installed an aftermarket IC and the IATs dropped and the power feels consistently there even on the super hot days.

[dradernh]

I'd start by putting Swaintech's White Lightning ceramic coating on all of the parts of the exhaust system that are helping to heat-up your engine bay, including the turbine-side of the turbo.

That ceramic coating made a big difference in under-hood temps on a turbo car I owned with power and weight similar to that of the M235/M240. The product is a thick layer of ceramic material, not the usual hi-temp paint with some type of ceramic material added to it. Specifics can be found here: http://swaintech.com/race-coatings/r...aust-coatings/.

A louvered hood will go at the problem from the other direction. I don't know if anyone is making such a product for these cars - not that you can't have general purpose louvers added yourself.

[Dylan86]

Originally Posted by Maynard

Doesn't the M4 have a water-mist sprayer to help cool the IC - that shouldn't be too hard to rig up, at least for a quick trial to see if it helps.

WMI, it's a beautiful thing. You don't require an upgraded intercooler either, it would just help with flow at higher boost levels. The stock FMIC is a peanut in size, FWIW. I did notice a performance bump with the upgraded intercooler, but nowhere near the gains that were had from adding WMI afterwards, it was night and day.

[230iZTR]

I thought the B-series block had a much better factory water-to-air intercooler setup integrated into the intake plenum. So heatsoaking is still an issue, but to a way lesser extent than it was in the N blocks. The M235/240 Racing appears to use the factory cooling setup too, so I don’t think it’ll have problems when you’re rolling.

If you get caught in a lot of stop and go traffic then a bigger set of fans (Spal, etc) and maybe some ceramic foil or coatings (Heat Shield, etc) on the tubing pieces you want to trap-in or keep-out the heat most. Last you could try upgrading the radiator to something bigger with more fins and higher heat capacity (CSF Radiatiors, etc) but I haven’t seen many people upgrading those yet, so I assume it’s either not on the market yet or the gains aren’t great for the cost.

I’m also somewhat skeptical of hood vents. You’d probably want something with an upright lip at the leading edge of the vent to stall the air above the vent and create a lower pressure bubble to suck the hot air out, but I’m not sure about what kind of placement would work best. You’d likely get measurably different results with it at the front / middle / rear of the hood and also relative to the centerline. Plus you’d have to custom fab it or adapt a stock unit from another car (eg Ford Mustang GT500) unless you wanted to pay the beaucoup bucks for the new M2 Competition M-Performance unit when it comes out. (Edit: the “power bulge” does not appear to be vented, so scrap that idea).

[dradernh]

Originally Posted by 230iZTR

I’m also somewhat skeptical of hood vents. You’d probably want something with an upright lip at the leading edge of the vent to stall the air above the vent and create a lower pressure bubble to suck the hot air out, but I’m not sure about what kind of placement would work best. You’d likely get measurably different results with it at the front / middle / rear of the hood and also relative to the centerline. Plus you’d have to custom fab it or adapt a stock unit from another car (eg Ford Mustang GT500) unless you wanted to pay the beaucoup bucks for the new M2 Competition M-Performance unit when it comes out. (Edit: the “power bulge” does not appear to be vented, so scrap that idea).

The photos below show both types of hood vents on an E36 M3 hood. The top view shows the layout, the side view how high the center vents stand proud of the hood, and the view of the car is to see the full aero package on the car.

The pair of vents standing up from the surface of the hood were placed a few inches behind the radiator on the center line of the car. While they did provide an exit for air passing through the radiator, their purpose was to increase front downforce by smoothing the passage of that air out from under the hood. The car didn't have issues with heat. Raised hood vents were used for the reason you suggest - note that they're fairly small, so they don't create too much disturbance of their own.

Admittedly, hood louvers are a last resort on a street car; my experience would lead me to start with Swaintech's White Lightning. I agree that uprated fan(s) and gold foil have their place, too. In the end, the trick is to spend money only where it will do the most good, and to stop when the problem is solved. One approach is to start by calling people who have already solved the problem. That is what's worked best for me over the years.

Hood Louvers – E36 M3 – MA Shaw Integrated & CF External – Top View


Hood Louvers – E36 M3 – MA Shaw Integrated & CF External – Side View


Hood Louvers – E36 M3 – MA Shaw Integrated & CF External – Corner View