So I have been thinking about this and wanted to start a discussion. With pulley sizes going into the stratosphere these days, and all kinds of concern with wobble, heat, supercharger bearings, and what have you - I think we need to figure something out. Do bigger pullies actually make these cars faster.

There are two local Kleemann cars. Both run 168mm pullies. I saw one a few months ago at the drag strip clicking off 122-123mph through the traps all night long. He's K2. The other has dyno'd extremely well (higher than me, I have 178mm pulley), although I don't know what he's trapped.

Then there are a couple of other cars. There's a 175mm VRP car that does 124-126 with the 600 package. There's also an EVOSport car running a 168mm pulley that has dyno'd in the same range as the VRP car.

Recently Powerchip had a dyno day with PC and there were two larger pulley cars (178mm and 180mm) that both did 430ish RWHP. They were both Stage 1 w/o headers. The EVOSport car I just mentioned with the 168mm and headers did 490. All these were after custom tunes.

Additionally, there have been RENNTech 55 cars with basic stage 1/2 that have also trapped very well (low 120s). My car, by having 10mm more pulley and generating the few extra lbs, should obviously trap higher, all things being equal, no? I have not seen definitive proof of this, but maybe I am blind, or maybe just have not been on the forums enough.

Please don't reply to this thread and say MORE BOOST = MORE POWAH, OF COURSE! If you know what you are talking about, you know that is not true. I am curious as to the real benefits of having over 175mm pullies. I am starting to doubt if there are any - with the exception maybe being a long tube car that loses a lot of boost - but even then I am not so sure.

So let's discuss. Post your experience. Tell us what you've seen. This could greatly benefit everyone especially since the pulley is really where it all begins for most of us who start to mod these 55k engines.

-m

 

Great thread, would like to hear more input as this will be my first mod on the CLS once it arrives in several days.

 

This is my experience and MY opinion in the e55 modding world. I too was confused and still am a little fuzzy on some things but here is what I have for you:

1) Every e55 is different!
2) Some 55k motors respond better and worse to mods? Do not know why.
3) Dyno numbers absolutely nothing! Tuning purposes only.
4) My car liked the 172mm pully way better than the 180mm.
5) Weather
6) Traction
7) Drags or street tires
8) Driver
9) Track

This is just my opinion on why some e55s are faster than others, at least this is what Im figuring out. And why different pullys do different things, and work better with certain cars.

Here's a confusing thing for you guys, I make less HP than a lot of other e55s, but I have a lot more TRQ than a lot of guys. My times show that my car should have abour 50-70 hp more! Weird!

 

A lot of this has to do with tuning.

 

Yeah, but um why is it so fast?

 

bigger pulleys do help if you have a larger throttle body, and headers.
Without tb and headers 175mm is the max you should go without going into the overkill zone.
Someone posted the S/C efficiency graph on this forums. basically after 180mm the benefits were detrimental.

 

I can not speak for all the other combos out there but I am a 177-180mm advocate!! That is the largest I would go though. Better to make power from other places after that.

Twin rear exhaust turbos would be a nice addition..

To be able to make 500 rwhp with just a pulley, shelf tune, cooling and 80mm tb is nice! BONE stock exhaust too! Pulley and 80tb were my first two mods. Car ran well into the 11`s on that set up alone.

People making 430 rwhp with 180mm`s have other issues IMO.

 

Very timely topic, M


My opinion is that there is a fine line that we are looking for. I have also noted all of the 165mm pulley cars doing well, PLUS they typically run less in terms of cooling mods as well. That tells me they are making equivalent power with less heat.
I said this before and I ma believing it more now that there will be different sized pullies for different setups. For daily driving and playing on streets / road tracks, I may actually like the better response and less heat of a 170mm one vs. my 178mm VRP.

The data should be showing soon as some members convert from the 168mm ones to larger ones. My guess is that their cooling setups will show the heat change. I doubt they will be able to run a small reservior and get good times anymore like you can with a 168mm

 

There are cars running mid 11's and better on a 168mm which i would guess pumps just the right boost for that setup.(tune, HEADERS, 82MM TB BIGGER HE). On the other hand, my car ran mid 11's and Im running a 180mm and off course my IAT'S are shooting up faster and higher than a 168mm..Correct? and my trap times as you guys can see are extremely low..i do have a bigger HE and believe me it helped.I have been told that with a 180mm and without a reservoir in the trunk i will be as inconsistent as it gets!. In My opinion I only see my setup getting better specially im still running a stock TB. I Mean how fast can we get off the spray anyway? Low 11's?

My dyno #s were not good at all 458whp 94 Degree humid NY SUMMER DAY. stock Heat esxchanger
On that same day anything smaller than 180mm could have done a lot better!!

CONCLUSION!!
For daily driving or if you are just driving around like if you were ''Tony Pedregon'' the a 180mm is not for you.

 

Maybe someone can do some math based in this info I got from some other site. then use our pulley sizes and SC RPMs instead.

EDIT: As far a I know the 2.3L supercharger on 55k's can spin to 18,000rpms or is it 16,000??



Upgrading both the supercharger snout pulley as well as the engine crank pulley has a multiplicative effect on the drive ratio. For example. a 4.4″ crank pulley installed with a 1.8″ snout pulley, compared to a 4″ and 2″ system will have the resultant drive ratio:

New drive ratio = 4.4/1.8 = 2.44 which is a 22% increase over stock. Thus the combination of two 10% pulleys (one at the crank and one at the supercharger) gives a compound and multiplicative result rather than a simple additive result.

Last thing I want to mention here is it is important to know the maximum reliable RPM for your supercharger before you overdrive it. For example if we had started with a car that has a redline of 7000 rpms, and a 4″ crank pulley and a 2″ snout pulley, and an eaton MP62 supercharger that has a peak RPM of 16000 rpms then:

The supercharger drive ratio is 4/2 = 2.0
At 3000 RPMS, the supercharger rpm = engine rpm * drive ratio = 3000 * 2 = 6000 RPMS
At 7000 RPMS, the supercharger rpm = engine rpm * drive ratio = 7000 * 2 = 14000 RPMS

Now since the supercharger still has 2000 rpms to go before it is maxed out then we know that we can overdrive it a little for more boost and more power. Typically overdriving teh supercharger to 16000 RPMs from 14000 RPMs would be a power increase of 14% or about 30 HP on an Eaton M62 (good power for the money for a simple pulley swap).

With the new pulleys:

The supercharger drive ratio is 4.2/1.8 = 2.44
At 3000 RPMs, the supercharger rpm = 3000 * 2.44 = 7320 RPMS which means we are probably making 15 more hp at 3000 rpms!
At 7000 RPMs, the supercharger rpm = 7000 * 2.44 = 17080 RPMs, which is 1000 rpms higher than the maximum recommended RPM from our charger.
At this point the supercharger being overdriven will have larger frictional losses, a higher power consumption to drive it, and much higher outlet temperatures. Definately not safe for sustained operation.

If we do the math backwards then 16000 supercharger rpms will occur at 16000/2.44 = 6557 engine rpms. Meaning that with this gearing you will gain power from 0 to 6500 rpms, but from 6500 to 7000 rpms you will lose power.

The warning here is that even though most people would be willing to trade off 500 rpms of high power (especially if it’s on a car that has it’s cams optimized for peak power at 6000 rpms for example and isn’t building power past 6000 and forcing you to shift early), for a low rpm torque and power boost which helps alot with in town driving and mid gear passing conditions. Aftermarket tuners know this preference and are not hesitant to overdrive your charger, so it’s up to you to make sure you are aware of this when you make the decision to do so.

 

My Math is wrong EDIT:

EDIT: what is the MAX this blower spins at?

13,500?
14,000?
16,000?
18,000?
The 55k SC with a redline of 6500rpms or so will spin the SC 13,000rpms with stock pulleys.
168mm pulley will spin the SC at 14,365rpms
178mm pulley will spin the SC at 15,210rpms
180mm pulley will spin the SC at 15,340rpms

Example of Math I used:

168mm to inches = 6.61 inches
76mm SC pulley to inches = 2.99

6.61/2.99 = 2.21

2.21x6500prms = 14,356rpms.

also thats not calculating rotational mass one pulley has to another

 

The smaller snout pulley on a serpentine belt system found on the M112K's will benefit greatly from not overdriving other parts on the belt system.

I've heard a few guys with that motor talk about not going to the bigger pulleys and those guys are still very fast.

 

Anyone want to swap a rennTech 168 for a VRP 178? It is the first rendition of VRP's pulley that came from Australia (thanks Finny!!)

 

The 180 mm setup along with the standard HE upgrade and rear-mounted reservoir seem to be the sweet spot for optimum pulley size and optimum performance.. From what I've seen so far, the quickest/fastest 55s in the country, especially ones running between 11.0 to 11.2 @ 125 to 130 mph seem to be using the 178 to 180 mm pulleys. In terms of reliability and effects on the supercharger, that is yet to be seen. But as the cars age, and more people add more mods, I suspect we'll be able to get much more data in terms of reliability. As one example, I believe Chiromikey has been running the 180 mm ASP pulley for approximately 100k miles with no issues, and I know two others that are at the 60k and 70k miles with the same pulley and also no problems (at least as of yet)

 

1 thing is for sure. LARGER PULLEY = MORE HEAT + LARGER OR ADDITIONAL INTERCOOLER

 

I think its tuning and IAT's.

Tuning: The bypass valve

IAT's: Additional heat

 

I am still looking to buy a pulley -- how much?

 

I have a few runs vs 180mm car, over a timed mile his car was faster trapping 165.77 but my car was quicker over the mile @ 162.54.

I was on 19s he was stock.

Paul

 

Agree 100%, from what I've seen/read.

Don't forget, chiromikey's car is primarily run at higher altitude (I think? Please correct if false). Should be less strain (i.e. "thinner" air) than a vehicle driven primarily at lower altitude. Regardless, the larger pullies in theory should cause greater wear-and-tear... but how detrimental of an impact remains to be seen, IMHO.

 

actual altitude is only 1225ft...da is another story altogether.

 

If you use a 168mm pulley how much boost do u get from that ? 1psi 2 psi ???

 

I thought 2 - 3 and then another when you get to 178mm, but not sure.

 

i think renntech make 2 pullies is 168 the largest pullie they make ?

 

What s/c speed does the 722 SLR achieve?

Any idea as to pulley and snout size and s/c gearing. This should be the best version IMHO....

 

Boost, changes from car to car from mod to mod, I have a 178mm and saw about 1.2 loss in boost when I went to headers, power went up but boost dropped. I guess it would be easy to check the efficiency of the supercharger by logging boost and changing to a bigger pulley and find were it stopped making an increase in boost.