All,

I'd just like to share my findings on taking apart my BBR 220 conversion one rainy after noon. (BBR is a UK tuner)

The pulley in this conversion is 52.5mm in diameter i.e. exactly a 20% reduction over stock! (as measured with a vernier).

The conversion also includes a MTH remap (marketed as their own brand !) which has a rev limit of 7,300 revs!

My car has done 18,000 miles since it was converted (05/05/2004) without a problem. It has done numerous open pit lane (6+ hr) track days and has NEVER missed a beat or thrown a belt.

I was getting a hell of alot of belt slippage though going up hills under a continous RPM load, the smell being similar to burning tyres in a fire coming from the engine bay.

Needless to say, I now have a GT tuning Phase 1 converion with a 63mm TB and it feels even faster than my previous conversion, probably down to the fact that the belt no longer slips!

If you have a 19% or smaller pulley, upgrade your idler tensioner (GTT sells a very ingenious setup) and change your belt every 10K miles if you drive hard.

Any questions, please just ask and I'll attempt to answer them.

Cheers,

Henry

 

I want 20% pulley! I have seen the article about BBR tunning. Very impressive! Too bad no one offer that kind of performance in US.

 

The BBR kits are a ripoff.

1500 GBP for a piece of painted aluminium, an idler pulley from an old Ford and a MTH remap which costs nothing anyway is OUTRAGEOUS!

Be happy with what you have your side of the pond. At least you have some repuatable vendors such as Randy et al.

Who do we have? Oh yeah, JCG and BBR One of them is a scammer, the other is in BMW's back pocket.

In all seriousness, If you want a quality idler pulley, talk to Roland at GT tuning here in the UK on:

+0044 (0)1258 455545

He will be more than happy to help, his prices are reasonable and he can ship abroad as well

Cheers,

Henry

Henry

 

the P&D "19"% pulley measures 2.070" dia

 

What are you trying to say JLM? I don't get the rolleyes thing.

So there is 0.00307" difference between the BBR and P&D pulley. What do you conclude?

Thanks,

Henry

 

the "19" % is in quotes because in effect it is really 20%

 

So how much boost pressure does the 20% pulley run?

 

The 19% pulley (Helix's P&D one anyway) I believe rounds to 20%. Plus it's only $100 or something like that. Quite the far cry from the thousands for the GGR. Don't forget about the TWO twincharged options here also. So don't fret about it. There are plenty of powerful performance options in the U.S.

 

I'm interested in upgrading my idler tensioner, A link to gt tunning would be greatly apreciated. Thanx.

 

Helix is upgrading this also. In fact, they're upgrading a bunch of stuff related to the pulley. I'd give Eric a call to see what they're doing over there.

 

I think you guys are missing the point of my post (or I didn't make it clear)


I drove around for 18,000miles with a 20% pulley on with a MTH remap with a redline of 7,300 rpm. I take my car to the redline pretty much every day (when joining the motorway x 2 plus burning off other cars) and the only problem I have had is a little belt slip going uphill but no belt breakage.

I have been on track for numerous hours at a time, flogging the car up to 7,000rpm with no problems.

The supercharger itself is in MINT condition after 23,000 miles (taken off the car on Saturday).

Basically, chipping with a 19-20% whatever is not that taboo. The main reliablilty issues with using such small pullies can be addressed by using an uprated idler tensioner. The BBR conversion doesn't even use uprated injectors.

The end.

Henry

 

Confirms what I've believed all along. Although there are other camps here who believe that the 19% is evil .

 

I will give helix a call, my 15% pulley was installed by Eric. I've got 30,000 miles on that pulley now and I'd be interested in having it inspected. I want to upgrade the idler tensioner and perhaps replace the pulley and belt if necesary. Thanx again Greatgro.

 

Just posing a question.

The 19% reduction pulley will no doubt generate more boost than a 15% reduction pulley. Furthermore, it generate more boost at lower RPMs (ie deliver power increases earlier in RPM range) than a 15% pulley reduction.

But wouldn't the real advantage over the 15% pulley only be down low in the RPM range? Here's my logic (please feel free to correct me/smack me down, as I'm just posting some randomn thought/logic).

We all know that the supercharger compresses air, the pressurized air then runs through the intercooler and then into the throttle body. We also know the need for the intercooler is because anytime we compress air (increase pressure), the laws of physics dicate that the temperature will increase.

And we are trying to get the highest density of air (oxygen, specifically) to the throttle body. Since density is directly tied to both pressure AND temperature, we now can appreciate the purpose of the supercharger and the intercooler. We want high pressure and low temperature.

We all know that the MCS was originally designed with the JCW kit in mind. Therefore, all components of the car were meant to handle the 15% reduction pulley, and other compnents of the JCW kit. So the intercooler was designed with the capability of cooling the compressed air coming off of a 15% reduced pulley set up.

The 19% reduction pulley would generate more boost, as mentioned above. But by spinning the supercharge faster, and increasing the pressure of the air, the laws of physics dictate that the temperature must increase. Has to. No way around it.

So it would seem to this shady-tree-mechanic/wannabe engineer, that unless you find a way to increase the cooling capacity of the intercooler significantly, the 19% reduction pulley would only be an advantage in terms of WHEN the power comes in. And in all honesty, would actually REDUCE power when in the higher RPM range (due to increased heat which negates the increased pressure).

So I guess my questions are really these:

To all of you with the 19% pulley:

Is the main benefit (in your opinon) access to power at lower RPM (i.e. more immediate response)?

Do you try to shift earlier in order to avoid the additional heat?

How many of you have altered your intercooler set ups to handle the heat? (i.e. gone to liquid set ups)

Just curious to see. Don't want people to think I am bashing 19% or 15% pulleys. People want different things out of their cars, and will modify cars to fit their own idea of "the perfect ride."

 

Nope. The supercharger is just displacing air. There is no compression whatsoever.


--
Cheese

 

I didn't know that. I assumed the JCW kit was made after the car, with the car in mind, not the other way around. Just my $.02 though...

 

I shift sooner---because I get to redline faster. But maybe that is not what you meant.

This may sound bizarre, but if a compressor (poor Benz even names its models Kompressor) could pre-charge a tank, then the motor could draw air from the tank and since it was then an expanding gas, it would enter the motor as a cold charge. Something tells me you would need a large tank.

 

It was always my choice to explain the effect of the 19% by imagining the torque curve in a typical dyno plot to be shifted to the left.

 

No. It is uneven though. Some of what you say is true with heat. The other thing you neglected to mention was the drag that the supercharger causes. The smaller the pulley, the faster it spins and the more power is needed to spin it. HOWEVER, you're still better off. The hgiher boost levels do compensate for all of that.

I'd say 19% versus 15% is a HUGE improvement at low RPMs (<4k RPMS), a VERY BIG improvement at mid RPMs (4k-5.5k RPMs) and a moderate-somewhat big improvement at high RPMs (5.5k RPMs to redline).

No. I do shift earlier b/c there is plenty of power available early and it is more fun to get power out of lower RPMs. It makes it feel like you have a much larger displacement engine which is a good feeling.

Not I. I don't think it's necessary. I don't think even the TWINCHARGED MINIs use a larger intercooler.

 

I'm running a Helix 19% pulley, and can second Greatgro's observations. I had to switch fuel brand to clear up a bit of a knock problem that surfaced right after the pulley was installed, but after the change in diet, WOW! Still on the stock plugs and intercooler, too. I haven't tried a 15%, and so can't speak to the 15%-19% incremental difference, but I have no plans to go back to find out!

I have noticed slight belt slippage at low ambient temps (8 deg. F the other morning- brrrrr) before the engine warms up. Under these conditions, even with a light foot I have to shift at 2500-3000 to keep the belt from giving the occasional chirp. Above 25F, this does not occur. I plan on adding the upgraded belt tensioner assembly (and idler, if one is released) once it is available from Helix.

As for the change in driving experience due to the pulley, the boost is available at very low revs, and the car is still docile and well-mannered at part throttle- so long as you can keep your foot out of it. I shift at lower revs than I used to, mostly because there's not enough room to really wring it out without either (a) running out of room, (b) running out of posted speed limit, or both.

The car just begs for stickier-than-stock rubber now. I have to turn off the DSC to feel the full potential of the engine, or else the DSC intervenes to prevent the tires from breaking loose. This is in spite of driving on S-lites shod with 205/50-17 winter tires. These weigh at least as much as the Pirelli runflats did, and place that mass farther from the center of rotation. Last year, this combination really bogged the stock engine; this year, the changeover had almost no effect, other than a somewhat softer ride.

 

Winter tires on the S really suck in anything but snow. The traction is awful - your wheels will slip or the DSC will engage with almost any amount of gas with a 19% pulley.