[bobbyggx]

Hi guys,

I am experiencing some slow acceleration with my 535i. The car goes from 0 to 100km in around 7 seconds or just about under them. This is on JB4 Map2, with Map 1 is a bit over 7 seconds.

Today, after pushing it and afterwards doing few kilometers cursing so it can cool down and I started logging on MAP6. Starting IAT was 123 F and I pulled from 3rd gear WOT from around 2600rpms. At 6300rpm the IAT was 145 afterwards I shifted to 4th and then for a second in fifth. The last recorded IAT was 183F, and I am sure If I continued pushing it it would have reached 200.

The ambient temperature was 29-30 degrees Celsius.

So, as I am suspecting the AC radiator to be clogged a bit which reduces the airflow to the inter cooler, thus brings the higher IAT which results in slow acceleration -> This is just my theory, as I couldn't find anything else wrong with the car.

Can some of you guys share his IAT in similar conditions and if he/she tracked the cars' acceleration 0-100. I looked at quite a few youtube videos where all 535i, stock, were reaching 0-100 in around 6 seconds or low 6, which is what it is listed in the brochure from BMW.

P.S. My car has 19" with 255/40 tires all around. I haven't measured its actual weight but I am assuming it is around 1850kg as I have EDC and Dynamic drive.
P.S.2 For those who are interested attached is the last log which I was referring to above.

[Slammin]

I've never seen a log with IAT that high! I did a WOT yesterday and it was almost 100F with 60% humidity and my IAT started at 118F and peaked at 134F.

Maybe your FMIC is clogged with bugs or road debris?

[bobbyggx]

Nope, it is clean. The issue is that the IC is between the AC and the Water radiators, I am running with the OEM IC still. The AC has high percent of the ribs moved aside and because of this it is blocking the air flow. I would take a picture of it tomorrow so you would have a visual.

My plan would be executed in two steps:
1. Cut the AC radiator with few cm. This would make the air flow directly thru the IC without being blocked from the AC radiator.
2. I am planning to run thru the free space new turbo ***** and mount a big FMIC (550x350x50).

[NorCalN55]

Originally Posted by bobbyggx

Nope, it is clean. The issue is that the IC is between the AC and the Water radiators, I am running with the OEM IC still. The AC has high percent of the ribs moved aside and because of this it is blocking the air flow. I would take a picture of it tomorrow so you would have a visual.

Not too familiar with the n55 535i, but certainly someone makes an upgraded IC that fits the OEM mounts. The stock IC, as you determined, heat soaks pretty fast.

[bobbyggx]

Yep, there are IC which can fit the OEM, but they going to be as efficient as a real FMIC with size of 550x350. This has already been done to a 535D car of a friend and it was quite a success. The difference there was that the AC radiator was taken from another car and the connections from the 535D were moved to it, while I will cut the bottom of mine.

I just wanted to confirm that my values of IAT are a lot higher than it should be, thus this should be the reason for the slower acceleration.

[bobbyggx]

Small update:

The AC Radiator cannot be cut because of the dehydrator, thus I bought a new AC Radiator with smaller size, but a bit ticker and I would make a hybrid.

Here is how the AC Radiator looks like:

[Bimmer_Boost]

Originally Posted by bobbyggx

Hi guys,

I am experiencing some slow acceleration with my 535i. The car goes from 0 to 100km in around 7 seconds or just about under them. This is on JB4 Map2, with Map 1 is a bit over 7 seconds.

Today, after pushing it and afterwards doing few kilometers cursing so it can cool down and I started logging on MAP6. Starting IAT was 123 F and I pulled from 3rd gear WOT from around 2600rpms. At 6300rpm the IAT was 145 afterwards I shifted to 4th and then for a second in fifth. The last recorded IAT was 183F, and I am sure If I continued pushing it it would have reached 200.

The ambient temperature was 29-30 degrees Celsius.

So, as I am suspecting the AC radiator to be clogged a bit which reduces the airflow to the inter cooler, thus brings the higher IAT which results in slow acceleration -> This is just my theory, as I couldn't find anything else wrong with the car.

Can some of you guys share his IAT in similar conditions and if he/she tracked the cars' acceleration 0-100. I looked at quite a few youtube videos where all 535i, stock, were reaching 0-100 in around 6 seconds or low 6, which is what it is listed in the brochure from BMW.

P.S. My car has 19" with 255/40 tires all around. I haven't measured its actual weight but I am assuming it is around 1850kg as I have EDC and Dynamic drive.
P.S.2 For those who are interested attached is the last log which I was referring to above.

IAT look normal for a stock or small intercooler. Timing is an issue so this is too much boost for your octane.

[bobbyggx]

Thanks for sharing! I was actually looking for someone who can tell me
If this is normal for my car setup.

The log attached here was just a small test, and it is may be misleading. The actual issue for me is that the car is accelerating, even with JB4, around 1 second slower. This is the reason to start looking for a problem but I couldn't find one and the IAT was the only thing. Now if you say that for stock iC it is normal I am out of ideas. So any other pointers are welcom and much appreciated!

Here is a link to my map2 log as I am driving with it all the time.

Map 2 log

[spammer]

Originally Posted by Bimmer_Boost

IAT look normal for a stock or small intercooler. Timing is an issue so this is too much boost for your octane.

I agree in my Novice opinion. Your car is pulling some timing and you're going very lean up top. I mean these cars run lean up too but it looks like 10 is pushing it. Get some 93 octane or drop your boost .5 until the car stops pulling timing and feels more consistent.

Trying to get a timing pull of 1 degree or less is most desirable.