Here's a plot showing the resulting boost plots from 3 different setups:

My '03 MCS, completely stock, on 1/28/03
My '03 MCS, 15% pulley, Alta intake, Magnaflow cat-back on 2/8/04
BlueMCS' '03 MCS, 19% pulley, BMP intake (?), Rogue dual exhaust 2/7/04



Interesting tidbits - the 19% makes more boost at 3k rpm than the stock pulley does at redline. The 19% pulley delivers about 2psi more than the 15% pulley pretty much across the entire rev range. The 19% delivers about the same boost as the 15% only 1000-1500 rpm sooner. Unlike Caddman's assertions, the 19% doesn't deliver anywhere near 25 psi, more like 17.5 psi. I have trouble believing that the frozen tundra of South Carolina results in an additional 7.5 psi of boost. I have a 19% pulley ready to go on, I'll do some back to back logging with my own car including IAT's. The above plot is a bit of an apples to oranges comparison since BlueMCS' car and mine are different. It still gives a rough idea of the difference between 15% and 19% pulleys.

Boost is good, huh?

 

Great information as always Andy. :smile: Your work is always appreciated. Boost is good. :smile:

 

Andy,

What's with all the data, and no explanations?

We want to know how many new dimentions of drivability were
added to the car with this mod. 3? 3.5? 4? Four new dimentions
would beat any existing vendor measurement.

I'm looking forward to the before-n-after dyno runs.

 

Those are impressive gains. Even if it's apples-to-oranges they're similarly equipped, and I wouldn't have exptected those kinds of gains for another 4% reduction. Did you get any chance to measure temps?

Thanks for taking the time to put that together,

Jeff

 

hey andy you really need to stop teasing us with all of your engine plots and give us the mini spec vag-com! please with suga.....

 

Holy BOOST, Batman!

Wow is the 19% pulley impressive. I can't wait to see some dyno plots of 15% versus 19%...

 

Let me tell you - from someone that went from a 15% to a 19%, the difference really is huge! Check Andy's graph - the 19% gives you the same boost at 4200RPMs that the 15% gives you at 6000!! Can you believe it? I can. That's 1800 RPMs sooner and we're not talking 19% versus stock or 15% versus stock either. That's just 19% versus 15%. So stop trying to spend thousands on polished heads, exhaust headers, cams, lightened flywheels, etc,...just to get a handful of extra horsepower. Upgrade to a 19% and get torque - tons of torque - more than all the about mods combined probably!

 

Wow GreatPro...you seem to be impressed with it...I haven't done the pulley yet and would like 19% but some of the stuff I have been reading concerns me as I know it does others as well...I wanna go 19%..but is it safe?

 

i have a friend here in miami florida that has been using a 19% on his car since the first week he bought his car, and its been about 3 months now with now problems at all, and let me tell you. THIS GUY DRIVES HARD!! ALL THE TIME!! he used to race in formula 3000... :smile:

 

I'll be the skeptic and say that much additional pressure at low rpms might not be healthy for the motor but only time will tell. Elevated cylinder pressures at low rpms generally isnt good for your rings/pistons.


--
Cheese

 

I am going to have to go with Cheese on this one. I think we will start seeing problems with them this summer. Everyone who says that they have had theirs for 3 months or saying that they have put on a hard 2,000 miles. Means nothing. That is way too short of a time to tell anything, plus for most of the US, it is quite cold.

I am going to have to go with JCW, AmD, and some of the other tuning companies who have invested a lot of R&D dollars, who have stated that 15% is the reliable limit on an engine with stock internals. When the heat goes up this summer and people are putting 18 lbs of boost on these engines, I think we will see problems. Even Randy doesn't recommend these.

I know that Helix has been doing some work, but my money still goes on a company like JCW who put over a million miles on this type of modification. One car that has been pushed hard for a few months, doesn't make the part reliable.

Obviously no one knows the answer and time will tell on who is right.

 

Andy -

I think that the graph says it all....you may be lighter but I betcha I'm faster!

Yea Cheese, I think you may be right too. I've heard that any pully'd car runs great until it hits 40k miles, then the head bolts melt.

Weeda - I think that the real myth here is the level of R&D dollars assumed (you know where to draw the lines dontcha?) put forth by the "big boys", especially on the pulley mod.

 

cheese; wouldn't your argument also apply to higher compression ratios and yet piston engines have operated with much higher ratios in the old days?

 

I remember something related to water pump cavitation before red line with a 15% reduction pulley. I run a 15% reduced pulley and just to be on the safe side Imake a point of shifting around 6800 rpm when pushing it so to avoid a problem that May or not exist. I hope some of you know anything about this and can shed some light. Only reason I bring this up is that I haven't heard anything about it mentioned on any of the 19% reduced pulley threads. Any takers? Thanx!

 

Can i put that chart on my site?

Those # are pretty good.

 

uh, Andy, what's up with those low PSI numbers?
during my baseline run, my 10/03 build MCS with Auto Meter Ultra-lite mechanical 2" 20PSI boost gauge tapped near the #1 cylinder intake runner on the intake manifold showed about 12.5PSI at 6950RPM - with the stock pulley. agokart has the video tape to prove it. Just running on the street with my 15% pulley, agokart and I have seen a bit over 17PSI on the gauge near redline. How are you measuring your boost? :???:

 

So are you guys making changes to your ECU's or are you just adding these smaller pulleys with the stock ECU/Injectors??

 

>>cheese; wouldn't your argument also apply to higher compression ratios and yet piston engines have operated with much higher ratios in the old days?


Yes, there are lots of factors that come into play like ignition timing, valve timing, static compression ratio. rod/stroke. etc all which will effect your dynamic compression ratio. Problem is we're changing one factor and not the others.... I'm not saying it WILL be a problem, but we're following the recipe :smile:


--
Cheese

 

Apparently these cars make varying boost levels, as my 15% pulley peaks at 15psi at 6900rpm, according to my Autometer mechanical gauge. It stays at the 12-13psi range from 4000 to 6400+, then abruptly spikes to the 15psi point right before redline. Since I rarely run it that high, I am considering the 19% pulley for a more useable boost range.

 

Boost, Boost, Boost... Thanks for the Graphs Andy everyone appreciates you work and look forward to your dyno results.

Seems to me that boost is what is making people think the 19% pulley is so great and so much better than the 15% pulley. I just want to caution about getting excited about boost. Heat makes Boost and Boost alone doesn't make power, air density makes power because of it's ability to burn more fuel. I think it's critical to know the dyno numbers and not the boost. People may be seeing 26psi of boost but I'll bet the temps are way up and it's not producing anymore power. I certainly not saying the 19% isn't producing more power than the 15% or course it is, just that the 19% pulley's power can be exagerated based on people looking at one factor and not the whole picture especially when that one factor can be a negative. The Boost is only as valid as the temperature at which it's achieved.


Wow 26psi of boost, just imagine the power I'm making...

Also, everyone is specualting about the reliability of the 19% pulley, I'll speculate also, I really don't think 4% is going to make that much difference in reliability of the 19% pulley, how often do you stay at redline anyway unless you have a dedicated race car? The major thing that will reduce the 19% pulleys reliability is going to be from heat. If you allow the engine to create boost from unnecesary heat you are causing unnecessary stress on your engine and that will cause extra wear on the engine not the mechanical reduction by 4%. Create more boost from 19% pulley and control the heat and everyting be cool mon.

 

friedduck wrote:
No IAT logging yet. I'll do that on my own car when I swap my 15% and 19% pulleys back and forth. :smile:

hondacivic wrote:
No.

hondacivic wrote again:
No.

Ryephile wrote:

These were logged from the DME, which uses the MAP sensor mounted in the intake manifold. The sensor measures absolute pressure as a voltage, which is then converted by the DME into mbar of absolute pressure. I converted that figure to gauge pressure by subtracting ambient and converting the units. It's normal for gauges to show slightly higher peak numbers when the boost transition is quick, the needles tend to overshoot a bit. FWIW, I have an Omori mechanical boost gauge in my car that has shown the same results as my logging, +/- about 1 psi.

Speed-Demon wrote:

All 3 of the above plots were done with stock ECU's and stock injectors.

 

>>My papayas-to-apples-to-oranges response is that my chipped '00 GTI 1.8T made 15 psi at 2k rpm in higher gears and it lasted just fine.

Fruity.

--
Cheese

 

I have done some IAT logging along with boost values with my 19% reduction pulley. The only issue is that the outside temperature has averaged about 13F. Is anyone interested in the temps as they relate to boost or vehicle speed?

 

if you have intake temps for the different pulleys then yes, i would like to now what kind of temps you are seeing.... :smile:

 

folks,
finally pulled the trigger.
i am a new soon-to-be owner of a 04MCS (just placed my order last week).

i have been perusing this forum for awhile now and i find the pulley mod to be the most fascinating mod for my upcoming MCS.
two questions i have about the pulley change:
1) just wondering about the gas economy tradeoffs in going to any of the pulley reduction schemes.
2) i have seen threads about changing the ECU chip.
any serious downside to not making the change?

appreciate any light those of you in the know can shed on this matter.

a mod newbie,
-spirit16-