Despite various unexpected maintenance costs for boring but needed items (oil cooling lines, power steering lines, coolant pipe), I am considering and my mechanic likes the LOWER SUPERCHARGER PULLEY for my 2002 XKR coupe that is among the last ones built with the Mercedes transmission and that included the upgraded secondary timing chain tensioners.

I suspect the upgrade is great for short blasts followed by mellow driving for a few minutes to prevent heat soak. So for a city driving person like myself who rarely has to drive during peak traffic hours that should be swell.

However, I'll bet sustained sport driving over a mountain pass at 8,000-9,000 ft (so 15 minutes hitting the engine hard) the cooling system will be incapable of preventing heat soak and the power increase over stock will be zero. AVOS and others have written extensively about our Roots blower limitations so that's pretty established, right?

Maybe upgrading to the blue-top solinoids would be a better upgrade?

 

I have the lower s/c pulley upgrade and I am very happy with it. I live in Texas (summer time highs are 100F+) and have never experienced the heat soak limitation that you described. That said, I also upgraded by intercooler radiator and my intercooler radiator coolant pump. I do mostly highway driving and I drive fairly aggressively. While I'm certain that if you were racing on a track you would exceed the ability of the coolant system, I really don't see this as a common issue even during spirited driving on regular roads.


Mark

 

Thanks Mark, what are the details on your upgrades re "intercooler radiator and my intercooler radiator coolant pump" ?

Did you do those at same time as lower pulley or later on?

What are your thoughts on the blue top solinoids for the Merc transmission?

 

I did the lower pulley, intercooler radiator, and coolant pump all at the same time. I got them from EuroToys. These guys are really good and will stand by their products. The new intercooler radiator is much larger than the stock intercooler radiator.


As for the Blue Tops mod, I have the parts for this but have not yet had them installed. I understand that it provides a much more crisp shift.


Mark

 

Are you waiting to do the blue tops for any particular reason?

Are there other things to do at the same time and thus you are waiting till those need to be done?

Based on other's advice, blue tops seem like a good choice to do first as I drive mostly in the city and canyon runs are an occasional treat.

 

Be careful with thicker intercooler radiators, the disadvantage of these is that they allow less air to flow thru, which not only limits their cooling capacity but also lowers the cooling of the condenser and engine radiator behind it. The one ET sells is even so thick, that it sits also way to close to bumper, limiting even more fresh air to flow over the unit. Attached picture clearly illustrates this (and also shows one I have made with a larger surface area).

If you want to improve the intercooler radiator, then increase the surface area at least, and not make it thicker. I had tested a 50mm once, but even that proved too thick, going back to 32mm was directly a good improvement.

This will provide you more cooling power, so less powerlosses.

With regards to the lower pulley, the power comes in much quicker, however top end the gains will be much lower (this overall still gives a good feeling you have more power, don't disguard that). But the hotter the charge gets the less the upper gains become as the ECU will pull back timing based on the temperature. As far as I know (and to leave a positive to ET), his lower front pulley is ok as it doesn't fix the damper/harmonic balancer part as some other suppliers do.


Just my 2 cents

 

My reason for waiting has nothing to with any upgrade strategy. I've just had some health issues this past year and just haven't gotten around to it.


Mark

 

For hot climates I would recommend a water/methanol injection kit to combat heat (Snow Performance). The larger intercooler radiators (either Eurotoys, or Avos's) add more of a Intercooler/coolant capacity which helps, but at some point that cooling affect would be overcome. For the street this would never be a problem, but if you planned on doing track days it could be.


I don't agree with Avos's radiator being any better than ours. It's not like we have the frontal cooling area of a Ford Superduty truck, most is hidden by the bumper. I have never seen any cooling issues on a XKR, or XJR with our set-up.


Yes, our 4.0 & 4.2 lower pulleys still retain their dampner properties.


Mike

 

Does being at a consistently higher altitude such as 5,300 ft through 8,000 ft above sea level factor into the cooling upgrades?

A few weekends ago I was having a good time driving over Loveland Pass but on the way down started getting "low coolant" warnings. When the car was cooled off, checked and found the level in the reservoir just fine. A few days later at the mechanic and he found a hose that had been leaking coolant and $550 later I had a new hose (over half of that the hose itself).

Ready to go hit Trail Ridge road, and I wonder what I would and would not notice with the lower pulley, which I plan to do with EuroToys, as his retains the harmonic balancing function. Having my car sit around for 30 days for the turn-around is going to be tough but I may have arranged other vehicles to drive in for work while I wait.

 

There are plenty cooling cores in the market. They affect flow resistance and heat exchange in different way, so that is not so simple.

Stock front heat exchanger has 50x28x3 cm core, that gives effective exchange surface of 3x50x28 = 4200 cm3

Stock two intercoolers have 27x9x5.5 cm cores, that gives 27x9x5.5 x 2 = 2673 cm3 of effective exchange surface.

My implication is: the best way to decrease charge temps is to produce better intercoolers which is not so simple They are the weakest part of the system. I'm not sure if placing bigger front exchanger would be a serious improvement. Have a look at the size of a stock front chargecooler, it's bigger than many main engine radiators of 1.4-1.6 petrol engines. I'm not sure if we need supersizing it.

 

2 cores behind each other will not double the capacity, remember, the 2nd one (or just like other thicker cores mentioned), will get hotter air already from the 1st one, so the cooling capacity left is already reduced. And next to that you lower the airflow, so again reducing the cooling capacity even more.

Anyway I use a 600x380 core, which is almost 70% larger in surface area then the stock one and the one from ET. I experimented with a 52mm thick core at 1st, but that was a waist of money, the 32mm one I have now is more efficient. The big advantage of this size is that it covers the full area as the main engine radiator, so when the engine fans come on, you use the full airflow capacity.

With a simple mod you can make also use of the stock engine fans, you only have to change the engine temp measurement (so a switch for example on the temp sensor line with a resistor that for example is equal to 97c, that will start for the 4.0 cars the fans at high speed, but the idea will also work for 4.2 cars). I don’t have this as the radiator I have now is adequate for my driving.

When on a dyno, I usually turned on the airco (as then both fans would come on) between runs to cool down the intercooler circuit, which not only helped, but also let me experience the time needed to cool down the system, with the radiator I have now it was the quickest by far.

PS For those that don’t go with my reasoning, I have good news, I have a 2nd hand radiator from ET for cheap.

 

How did you check it?

 

The iat#2 values (so temp sensor in the intercooler) are unfortunately not readable; it gives an odd voltage that you would have to convert.

I Have also used an 8 channel tmp sensor system (which was normaly intended for PCs) and his way I could measure different spots whilst driving, But I have no data left of it unfortunately.

But normally (when on the dyno) I just use a infra-red thermometer, that way you can measure different spots very easily.