Superchargers...Whipple 4.0 or 5.0 vs Roots 14-71
 

Can someone explain the difference between a Whipple 4.0 vs their 5.0 ??? Keep in mind this must be for a dual carbed version. I have looked on the Whipple website, but unless I didn't navigate it properly, I could not find anything on the 4.0 as I did with their 5.0 and I am currently doing more searches within the archives of OSO about Whipples and the experience others have had with them.

Not really trying to beat a dead horse here, but I am transitioning from NA to superchargers and I am on a learning curve here when it comes to blower type/style power.

I am going to copy and paste an interesting comment from an OSO member (Airpacker) that sparked more interest from me....it's from another/previous blower thread and I thought I would put it on this thread.....

Airpacker, All that being said, here's the big question for me----If you remember or have any data, what kind of RPM's were you seeing at idle in NUETRAL and what RPMS IN GEAR at lowest idle on your friends engines with the AFR 357cc heads??? I am thinking of going with the AFR 335cc CNC ported heads---because I know they would create more port velocity i.e smoother idle quality, but if these Whipples are what I am thinking they are, then perhaps a AFR 357cc CNC'd might be the ticket WITHOUT sacrificing the idle quality that I am looking for...???

For example, with everything else remaining the same on a CARBED engine, if we were to swap out a Roots version blower with a Whipple, would the Whipple have a better idle quality over the Roots just by design? (let's say 557cid w/a Roots sytle Blower Shop 1471's destined to make peak power @6000rpm) Is that possible?---while still making power peak power @6000rpm? Will it do that? Or is my goal unreasonable?

If a Whipple will give me the results that I am looking for, then perhaps I will consider the change---especially with the idle/drivability quality I am looking for----it creates a lot of questions in my mind.

Sorry for being so long winded---btw, I have edited this post from its original form so as to try to condense it a little better. Anyone with any Marine Application Whipple supercharger experience/knowedge is welcome to chime in here especially as it may relate to a Roots version. Thanx

sorry for the delay in answering, been away sledding in the far north.

The motor is mefi4 injected. It idles at 800 all day in gear or out.

We went with the 357 for the power making ability up top knowing that port velocity really means nothing on a blown motor.

I would bet the difference between the 335 and the 357 was 100hp at 6000.

I don't really think the idle quality is a result of using a Whipple so much as a less radical cam profile coupled with the good fuel and timing control which efi can provide VS carbed.

I run a 420 mega with twin throttle bodies and plate injectors on my 900 and it idles smooth as silk with the same 268741 cam.

Thanks for your response especialy what you have quoted above. I keep hearing the cam profile is still going to be the most important factor for determining idle quality whether it's a Whipple or a Roots.

Also, I just could not find the 4.0 Whipple on their website and was curious if it was made for a dual carb installation such as their 5.0.---or only a single carb install...???

As stated, the cam plays huge part.

I think a wet intake, whether on a roots or a screw, would have to be comparable idle wise. Now a dry intake, say with port injection, I can see that being a better idling setup.

My buddy is running a blow thru procharger carb setup, with a big chiller. He called me and was telling me they had a really hard time getting it to idle correctly. I asked him if he was feeding the chiller with water at idle, and he said yes. I told him to try bypassing the chiller and see if it helps the idle.

I dont think they tried it, or plan to try it. They told me it shouldnt matter because its not a roots blower. My theory on that goes from back in the day when port injection was only a wet dream. Factory carbed engines all came with things like exhaust heat riser tubes, coolant thru the carb base plates, electric heated coils under the carbs, all kinds of gizmos to help them run smooth when cold. Heat in the intake helps prevent fuel puddling. Hard to get heat in the intake if your pumping air thru a chiller, then thru the carb, then into the intake, which is being cooled by 60 degree lake water. Shouldnt matter whether its blow thru, roots, screw, etc. Just my theory. Could be way off.

so are you saying that given a choice, a larger runner would outperform a smaller runner (within reason) for blower applications? I know most say N/A normally the smaller high velocity runner outperforms the large runner, but I can see what your saying in a blown application.

when i did those motors i told joe we should change the plumbing to a force fed through hull pickup,he said procharger recomends running water through the cooler even at idle,BEATS ME?

As far as I know, the 4 Liter is not offered in a top entry (carb), only in the rear entry axial blower.
The Whipple will idle better (especially with a carb) than a roots blower simply because of the bypass. I have done quite a few carbed 3.3 Whipples and they all idle like a 500, even ones with some pretty stout solid rollers and dry pipes. None of them had any blower surge at all.
If you take the bypass valve on a Whipple and hold it closed so it doesn't work, you can make it hunt at idle just like a roots engine will. That's why you see guys trying to retrofit a bypass valve to PSI blowers.....to make them idle better.
Eddie

Thats what he told me too. I dont see why they would recommend that. I can see it on say a 502 mag MPI, or something like that, but on a blow thru carb? Weird.

I would totally agree on doing the separate hull pickup for the chiller. I have some GIL strainers he can have if he needed them. They are the older style ones with the wing nuts around the lid, not real fancy but the price is right! :drink:

Very interesting. The more I learn about whipples, they really seem like the way to go from all aspects.