Hi all

Having fitted my new head (RMW) the boost pressure has dropped (expected due to big valve head, is not due to a boost leak!)and now I am thinking of upping the boost more by switching to a 17% pulley.

Just to get a collective answer does anyone see any disadvantages from switching to a 17% pulley? (or advantages apart from more power)

I initially went for the 15% as this is at the top end of the operating scale for the s/c before excessive heat is produced and it seemed the safer option as I had stock I/C (since changed to GP I/C).

James

P.S I will be having Jans tune and was wondering about the extra rpm of the S/C with the 8.2k redline, will it be better to keep 15%?

 

At least for us, the 17% reduction is by far the most popular total reduction that we sell.

My opinion would be to replace the Crank Pulley vs. the S/C pulley to gain the addl 2% you need. Something like CLICK HERE easier to install vs. a new S/C, gains addl. hp through the lighterweight and is safe and easy.

Jan should be able to compensate for the larger pulley. Although the redlin move, may need to be shortened a bit. But you will have MORE low end torque and HP vs. the 15%.

Let me know if I can help in anyway!

 

I have read about crank pullies and they sound a good idea but in the back of my mind I don't think I would fit one due to the fact there is no damper on the aftermarket ones and the undampened harmonics can cause pre-mature oil pump failures.Whats peoples experiences/thoughs on that?

Might end up sticking with the 15% pulley and see what its like after Jan has tuned it

Regards


James

 

Adam:
Tell us about crank pulley risk and install.
1. Is this easier than a S/C pulley swap, cause that wasn't too bad.
2. Is this really safe for the engine to replace a crank damper pulley design with a straight non-damper pulley? I have seen some debate on this topic in other posts. Do you have a mini-damper design that still has some damper capabilities, but maybe not the full weight savings?

 

I would swap out to a 17% and Jan will tune accordingly.
Will get a bit more low end torque. This is currently what I am running...

 

I would first wonder why your boost dropped? Compensating for the loss be going to a higher % pulley is a bit like putting a band aid on a cut that need stitches. You may want to find out why this happened first.

 

Whats you redline set at? I like the sound of an 8k redline though

 

What WHP or BHP are you running?

Also do you have any sound clips, would like to see what Jans header and exhaust sound as I may end up buying the header and exhaust if it is not too loud

 

Man your car screams.... How is everything with it after the scare?

 

It drops because of the head, bigger valves, more air flow, less pressure. This I know because it happened to me and others after the install.

 

This boost drop is a good thing and expected. The boost is only a secondary parameter, what is of primary concern is hp and torque, as long as they increase.........lower measured boost pressure is OK.
Nothing was actually lost here, there is no more or less reason to move to a 17% effective or direct SC pulley reduction before or after the RMW head.

 

Boost means nothing. 10 psi on one car will give you the same power as 6 on another. As for why it dropped, which do you think sees more pressure, a sippy straw or a cocktail straw? When you expand the volume that a given air output has to travel through overall pressure will decrease.

You've made the head breath better, thus the SC isn't working as hard to force boost through your engine. Therefore even though the total volume of air has remained the same, the boost has decreased (less effort).

For the record, here's what 10.6 PSI of RMW Boost will get you now adays.



You're kidding right?

 

And please, for the love of god don't put a freakin crank pulley on your car.

 

here is the same video on

 

Video link fixed...

 

I still would like to see some conclusive scientific data on the 'damage' caused by crank pulleys.
It seems to me that most of the reports are based on anecdotal evidence.
Just my 2 cents...

 

I am aware it is a good thing and it should happen after fitting a big valve head, but was wondering if it is worth fitting an even smaller pulley to increase boost a little bit. Although it is not too important what boost pressure it is, it is more important in the quality of boost.

Thanks for all your comments

 

I have seen 6 motors have broken oil pump gears and the ONLY common denominator was the crank pulley. Just remember we build engines and we won't sell you one with an aftermarket one on but if you want to improve our engine sales... feel free to do so

 

What was the whp numbers of that video I couldn't quite see. Somewhere in the region of 245?

 

that run was 249whp

final was 217 ft lbs of torque and 252whp on 10.5 lbs of boost

 

Very good power made then

Can't wait to see what mine can make next thursday

Once Jan has done the tune and he is happy I will be doing a back to back test with some racing oil to see if an oil change can give me a gain in hp. I will post the results next week

 

You'd gain more power (Weight loss!) by wearing no socks that day. This isn't a racing application, you're not going to gain 5-6 HP from changing your oil. The design tolerances on these engines are wide and varied.

As Jan mentioned, the final outcome was just north of 250 HP and 217 lb-ft of torque at the wheels. Here's the second to last dyno, easier to read when it's not in video format I suppose:



If you look at the results you can see that the car makes 180+ lb-ft of torque from right above 2k rpm's all the way to redline. Horsepower also, 200 WHP from about 4800 RPM's with a peak of 249 whp at 7244 RPM's.

It has a very meaty curve .

 

So what componets are added to this car to make that HP?

 

Jan will have to let that cat out of the bag.

 

RMW kit stage 1