I have a stupid or lets say ignorant question: Is “boost” analogous to pressure and “flow” about the same as volume (CFM) or am I just completely lost?

 

i think someone needs to get kenne bell to make a bolt-on s/c for us!!! i'll modify my hood for that! i'm sure it would cost much less than the slr s/c.

 

About time someone said the Kenne Bell name.

 

my friend replaced his S/C with an SLR one, when they were side by side, it was showing SLR is bigger, and when he installed it, his car became Lean, ><, his A/F ratio was 12.5 and after installing the SLR S/C it became 14.5 @@.

it wasn't tuned after the installation.

could it be that the SLR S/C was pumping more Air in the engine and thats why it became leaner !?!??!

 

Oh its been said years ago. We really need to come up with something though. Problem is there's not much of a market for the 55K so an aftermarket blower will be a one-off or just a few made all at once. I tried to get one built before with Victor but nothing came of it.

Perhaps, but without a tune the ECU will be trying to compensate so there's a lot of variables at play.

Interesting that when they were side by side the SLR was bigger.
Can you ask him what specifically seemed bigger, what the boost went up too, and if he tuned it by now?
Thanks and any info you can get will be much appreciated!

 

This is a fantastic thread on a topic that I too have often thought about...how to increase SC efficiencies. The idea of the Kenny Bell roots type blower is something that may prove to be worth while; however the cost to produce it versus the market for the application may not seem appealing to them...whipple may be another route..OR somehow taking a factory blower and sending it to get modified, perhaps internals, fin design, etc...etc...this last idea may be the most cost effective but don't know of anyone doing this sort of modifying superchargers kind of thing??

 

Yeah, this has always been an interesting topic for me along with custom top mounted coolers. I'll speak with Evosport to see if they can work some magic. There has to be a few people here in Cali that can help us get more boost from our blowers or from a whole new set-up.

 

a problem later on was accuring, the S/C wasn't turning on @@, tune problem, he took it to another place to tune it.

i don't know what happened to the car later on. it was orginaly MKB 620hp wide body. and he installed the S/C and a 172mm pulley on it.


sorry for no data about it.

both the S/C had diffrent #s and they were not the same size.


do some one know about the S/C pulley has diffrent sizes ?

i recall when we were measuring any 55k randomly, we found 2 different sizes

can some one chime in ?

 

Havoc,

I apologize for the long post but this is a complicated subject that needs to be stated clearly.

Boost is a measure of pressure built up in your intake manifold. This pressure is created obviously by your supercharger compressing air and forcing it all into the engine. Now, the relationship between boost and flow is obviously important, but you do not necessarily want more boost.

In the case of your engine - and please correct me if I am wrong - you have opened it up to 5.7L along with different cams and heads. This allows your engine to flow a lot more air than a factory 55 engine. I'm sure you have seen people comment on how their "boost" drops significantly when they add long tube headers to their car and they scramble to get boost back up because they think the drop in boost is bad or somewhat unfavorable. That is not true, and upping it could yield counterproductive results. Our blowers have RPM that is directly related by gearing to our crankshaft RPM. We therefore are (almost) always spinning the blower at a set rate as compared to engine RPM.

I don't want to start breaking out all the equations here, so some of these numbers are being done without a calculator. We'll use some hypothetical numbers on a makeshift engine... let's say at 5000 engine rpm, the blower spins at 10000rpm and generates 1000cfm of airflow (again, hypothetical round numbers for ease of discussion). This 1000cfm of airflow creates positive manifold pressure of 10psi.

Now we take an engine that has been modified to increase it's airflow and can now consume 20% more air from the supercharger at the same RPM. So at 5000rpm, the 10000rpm of the supercharger now only creates 8psi of pressure because the engine is pumping the extra air that would have created 2psi without allowing it to create pressure in the manifold. The supercharger is still flowing 1000cfm but the supercharger now only creates 8psi in the manifold. This is a good thing, a very good thing. When people assume they just need to stick a bigger pulley on their car to get boost BACK up to a certain PSI they may not always realize that spinning a blower at higher and higher RPM has an effect on it's efficiency and just because it will flow more air at a higher RPM does not mean that extra flow will translate into more power. This is where the compressor map comes into play. Even flow is not an absolute rule of power, some flows are better than others.

The bottom line is - when you are saying you want to create 25psi in your manifold - I am saying that shooting for a boost level is misleading yourself. You want to shoot for a flow number and a certain volumetric efficiency level - or in other words, you want to shoot for the POWER. If the 722GT makes 800hp at 25psi, do you care if you make the same power at 15psi? No, you want that 800hp at the LOWEST boost possible. You don't necessarily need to make 25psi to generate that kind of power.

I think it's a valid question as to how the SLR makes the power it does, and even how it makes that much boost with our same supercharger, but I don't think you should be setting your goals on duplicating it's boost figures!

Good luck,

-m

 

I just don't see it costing as much as you think, especially since you do so much of your own tinkering. You want to do an engine swap which to me is almost just as involved.

The most difficult part is find a place for the snails but I'm sure there's room somewhere for it. Properly spec'ing the turbos will be important and then the plumbing for intercooling/etc. Tuning wouldn't be that different than what you have now...

-m

 

Marcus I've been told just the opposite for going TT on a once supercharged car, in Ahmad's case maybe different but for going from say a 55K to a 55TT the tuning is where the problems are anticipated to be...spoke with a very reputable source about this...even with standalone on a 55K car you'd have to consider things like ABC, SBC and the other stuff the ECU/TCU controls

 

Why do people keep saying the ecu is a stumbling block to twin turbos, or even a bigger supercharger?
Boost is boost. Not saying it would be a walk in the park, but would it really be that much more challenging than converting an NA 55 motor to S/C'd?
Not trying to start something, just was curious if there were specific reasons people always say "trust me the ecu is the problem"...

 

I have one on my car. The old Kleemann sc was built by autorotor. Guess who else used autorotor back in the day. Yup, Kenne Bell. The old Kleemann sc is equivalent to old Kenne Bell 2.2L blower. Now go on youtube and type in kenne bell 2.2 and see what comes up. See why I want a lower compression motor now? 10PSI is childs play on this blower!

In order to take full advantage of a turbo setup I would need a lower compression motor to run more boost. Although its true I would gain power from parasitic loss at same boost level. It's tough because the people I know that can do the plumbing etc work slow and I don't like having my car down. Turbo is the way to go but I think 550+whp is very possible with my charger, if not 600+. Who knows what will end up happenning with my car

 

Sunir,

Ahmad's car is not like our car. He doesn't have to worry about supercharger bypasses and clutch engagements. He also does not have ABC or SBC.

-m

 

I hope to find out but just enjoying the car as-is with 6psi for another week before I proceed with project WTF.

 

I've been hearing that for like 2yrs now. If I had a motor it would be done in a weekend

 

Rather than trying to make a new aftermarket SC for the 55k. I think it would be better to rework the gutts of this blower. Like... Could you fit more aggressive rotors inside the stock blower? Could you rework the gearing inside the nose drive?

I've said it before, In an email I got back from Whipple they didn't rule out a set of their rotors fitting into the AMG SC.

As a forum we've been good with working with what we got. I know a bigger SC would be awesome. However maybe we should look inside our blowers first.. See what we can do there. IDK? just an idea.

 

Marcus,

No need to apologize for the lengthy post and thanks for your input and concerns. However, this is not a complicated subject bro. I never said that I think the drop in boost is bad or somewhat unfavorable and I understand that spinning a blower at higher and higher RPM reduces its efficiency. I also understand that it’s best to have peak hp at the LOWEST boost possible. Again, I get all that.

Now to explain from your previous example, I’m taking a car that makes 800hp with 10psi over one that makes it with 30psi. Then I’m increasing the boost from 10psi to 30psi and making 1,000hp. Of course you can say well I’ll take a car that makes 1,000hp with 10psi over one that makes it with 30psi. However, I’m going for max power to include modifying the engine as much as possible then throwing large amounts of boost to it.

Thanks bro!

 

I agree and would be interested in this approach... look within first to harness true power...sounds like something Dr. Phil would say lol

 

I agree!
We should look inside our blowers first. My car will be down for 3-4 months waiting for Titanium connecting rods to be built so I can donate my blower and have Evosport try their best to find a way or find someone else to rework the guts and fit more aggressive rotors inside and/or change the gearing inside the nose drive.

 

It’s going to be tough to fit more aggressive rotors inside since there’s not much room for improvement.
Like Finny said, “I don't think a bee's dick will fit between there”.

 

I'm sorry to take this even futher OT. I don't think making boost is the problem with our SC. Cooling down the AIT is the problem for our car.

The last two weeks I have finally turning some wrenches on my car so I now have a little better understanding of the working order of the SC of the E55. The way I see is:

-Bigger pulley, 200mm or even bigger (Sunir said something about 210mm pulley before) this will take care of the boost problem
-bigger injectors, from SLR 722 (should be plug and play so we don't have to worry too much about tuning)
-cooling solution, until someone can come up with a front mount air-to-air it'll be meth/water injection. We can run eight nozzles, one on each runner.

That's it for now.
-

 

Cooling solved.. Just get a good fab shop to build you some coolers. I've had these custom top mounted coolers built for some time now.

Time for more BOOST!!

 

Did you gut the OEM I/C under the blower?

One thing with I/C... again bigger is better but only insofar as you are able to add timing ... if you are running a smaller I/C and the engine does not pull timing adding a bigger cooler is not going to help much with max power - maybe some thermal efficiency ....But now I am not saying your setup will not yield better results... it should ... but it may not result in more power, but you will be able to use the power non stop I would hope.

Given the volume of those I/C's I expect you will need a significant increase in boost to get back to where you are before all else being equal in terms of volumetric flow etc...

Lets face it the only nett difference between a Stock SLR motor and a highly tuned motor from this board is not the power output (ok mbe there is a 20-30hp gap) but the SLR can deliver the power non stop alll day... clearly the SLR motor has been completely engineered for purpose - ours too but for a different purpose.

 

No, I fabricated a whole new "open" unit under the S/C instead of gutting the stock intercooler.