speedemon46

So Im driving down the interstate when low and behold I see a Bmw 335i creepin up behind me. So I decide to make him play catch up to me for about 1-2 miles with no issues. Needless to say he finally catches up to me due to traffic. Once traffic cleared I decide to shift down to 3rd gear (i'm going about 70 mph) while the 335i is right behind me practically tailgating. So I step on the gas and nothing...I mean my rpms are going but my car is slowly picking up speed, so i shift up to 4th and the response is better but still felt slower than usual. I did end up leaving him behind a few car lenghts but I think something may be mechanicaly wrong with my car. Has anyone had this issue before? BTW I do have aftermarket rims and tires (20x9s in the front & 20x10s in the rear) and they do rub on the wheel wells cause I can smell rubber after accelerating over 70 mphs. I dont have any issues when Im driving in the city my car responds normal.

skratch77

our cars are not that fast in 3rd and def not in 4th bro,try racing him from 40-90 in second gear and see what you do to him.

You could have a bad pump also and the tires rubbing is because the car lowers at around 80mph

shardul

iTrader: (1)

typical case of heat soak and s/c shut down

efivefiveamg

^yup

harjothundal

I agree, SC shutdown... Happened to me just once and the car felt slow as shiet... Also, why downshift? I just leave it in sport mode and floor it, my 55 always takes off like a bat out of hell when flooring @ freeway speeds...

BlownV8

Plus 4. Heat soak for sure. Intercooler pump probably needs to be replaced. Good time for an upgrade.

pearlpower

I had this happen to me once and it was not heatsoak or anything else. I downshifted and NOTHING. It could barely keep the speed. Then it all came back once I upshifted. It has never repeated again. The car just has these weird flukes from time to time.

speedemon46

Thank for the replies. Thought it was just me... Its happened a few times but only after driving at high speeds over a period of time.

Jakpro1

The Achilles heel of the near perfect car. Horiffic intercooler design.

We all die this time of year. You learn to live for cooler weather and do the best ya can.

speedemon46

Where can I get an intercooler pump upgrade?

AWOL

johnson cm30

they are ~$150 if you look hard enough

VCA_AMG

+1 on the SC issue.

But I gotta ask...

20's weigh considerably more = slower acceleration

20's rub and burn tire rubber off the tires = slower acceleration & accelerated tire wear.

Are they really worth it?

E55AMGGG04

3rd switching to 4th is the worst but end of 4th switching to 5th has proven strong for my car to say the least in runs against a w211 E63 and w212 E63 both up to 160mph.

To the OP I had 20's before also and it was noticeable power loss cauz I bought some heavy wheels at the time. Definetly check the PUMP that was killing me. I never knew wat the hell the problem was till I became a member and that magic CM30 pump made all my problems go away

pearlpower

20s do not necessarily equate to slower acceleration. I have had light weight 20s in the past which were lighter than stock by a wide margin and improved my acceleration on various cars. It all depends on the wheels and keeping the overall diameter the same. I just do not run them on the E due to all of the damage they received from the short sidewalls.

VCA_AMG

Unless you've altered the transmission gear ratio, 20's will be slower due to a small but still legit roll-out change as well (more top end, less acceleration). And lightweight 20s tend to be rare.

Curious if the look is more important than functionality.

tgoss

Nope, but hot dayum they look so good on these cars.

Stay with 18's if you're dead set on performance or get some nice 19's if you want a good balance.

pearlpower

The stock 18s on this car are on the heavy side to begin with so if one has the cash and is inclined, finding lighter 20s is very possible though options are more limited. One must also keep in mind that weight is not the only factor, but also the weight of the rim (rotational mass) is further out, and tire choice all play into the equation.

So, yes, generally, 20s would not be a good idea for performance, but as stated, the stock 18s are not light.

Rolling diameter is all dependent on the tire chosen. The common 20" upgrade people run are 275/30/20 which is 26.5" in diameter vs 26.3" stock, a difference which can be more than made up depending on tire brand itself as tire makes vary in width, tread depth,etc. A wash.

Even my current 19" wheels are 29lbs lighter(total) vs the stock 18s. On my last car I had 20s which were 19lbs lighter (tire/wheels total) vs the 18s and the car was lighter on it's feet due to this advantage.

Many variables involved. Either way, even if the OP was running 22s, the car would still go when downshifting and what he described is not tire size related. Most likely the pump/heating.

VCA_AMG

Excellent points & I agree 100%.

I enjoy the looks of a nice set of wheels, but I'm more interested in "freeing up" performance where I can. Adding increased rotational mass at the ends of the suspension arms doesn't seem like a place to start for handling or acceleration purposes.

Mantooth

Yes, they're worth it to me.

+whatever on the I/C pump. Mine went out not too long ago, too.

juicee63

+1

harjothundal

Is it possible that the slow acceleration may have been due to the vehicle adaptations learning your driving style?

For example, driving at a consistent speed on the freeway... The car learns your driving style and works with it... Perhaps that's coming into play too? Though, I've never had this problem... I don't drive my car hard by any means at all, I treat her fairly well with most strain from freeway on ramp accelerations or overtaking... Still, with my easy driving style, everytime I floor her or "kickdown" she takes off every single time...

speedemon46

Thats not possible since Im always hauling ***. It's hard not keeping my baby under 80 mph...lol though its a good theory...

speedemon46

Just ordered the part..next question is should I order the heat exchanger while Im at it? And are these parts DIY compatible?

pearlpower

Might as well do both together, get it out of the way. Easy to do ,remove bumper,etc. There are a few DIY posted up on this.

Fast55

+2 if you're really intersted in going fast. Yes, there are 20's that are lighter than the stock 18's, but you won't touch the weight of a light 18 and you will notice the difference. Race cars do not have large diameter wheels for a reason. Something like a HRE C20 with a nice lip still looks good and is several pounds ligher than the stock wheel. As far as the pump, you can just do a swap, but the intercooler setup is a POS as Jackpro points out. It's a little work, but can be DIY.