SC14 supercharger blow through

[bullzed]

I'm just curious as to whether this may be a realistic future project.

 

I'm running a 2.7 litre L26 with triple dellorto DHLA40's and it's supposedly had about 7k spent on the head and block by Datrally.

 

Would it be possible to mount the supercharger down where the aircon compressor sits and then have a blow through setup with a custom airbox running through the DHLA40's? It'd need re-jetting of course, but my main question is whether the carbies would be able to take around 5 - 6psi of blow through pressure?

 

EDIT:

 

I've done some more research and I've come up with the numbers of 1430cc of air displacement per revolution, they were initially set up to spin 1.25 times per 1 crank revolution. Now taking that into account, at 6000rpm, the supercharger is doing around 7500rpm, giving it a flow rate of about 11000LPM, that's around 390 CFM.

 

Now I realise that because of belt size and what not the pulley ratios are going to be out, but assuming I can get it to run at around 5 - 6 psi, would it be safe? Would it even be effective?

[nizm0zed]

yes, the dellortos can be set up to run 'blow through'

As for the choice of supercharger, i would recommend you buy a Eaton charger instead of a Toyota SC charger.

You can get the M62 charger from several factory cars, including the Mercedes C180 and C200 kompressor, that is pretty much perfectly sized for a low boost setup.

Or you can get the M90 from the VR-VS era commodore V6 motor.

Look on ebay.us for the best prices and variety. You'll find Eaton chargers going for a comparable price to the Toyota chargers.

The big advantage is the support for Eaton chargers, eg bearings, oil ect ect.

Ideally you want to spin the blower as slow as possible to get the boost pressure you want, higher RPM = higher inlet heat.

The Toyota chargers are a straight Rootes style blower, quite inefficient and great at making heat.

the Eaton chargers run cooler and quieter. they are still a 'Rootes' design, just a very efficient one

A whipple screw charger would be ideal but easy pay $1400 just for the charger.

The other advantage with the Eaton (and most whipple/screw) chargers is the inlet is on the rear of the casing, making it easier to mount in smaller places.

To get your boost pressure you do it 2 ways, 1st, obviously correct sized pulley, but secondly the more important way is to make the engine breathe!!!!

By opening up the breathing of the motor, particularly the exhaust, you'll actually lower the boost pressure the motor sees.

The charger still flows the same amount of air, and you still put in the same amount of fuel, but you make the engine work more efficiently, which equates to more power and lower temps.

Again, on temps, you'll find that the fuel atomizing in the airstream will actually cool the charge, so with some careful consideration you wont need an intercooler at all.

 

 

[be-zed]

bullzed you may want to google a mob called CARTECH . They may have something that could interest you with a triple setup blow throw.It is for a turbo but I see no reason why a super could not be fitted.

[bullzed]

Is the setup for the dellortos expensive?

 

I've seen a lot of the SC12 and SC14's around and I'm finding it hard to find any Eaton blowers. Would you highly recommend finding an Eaton M62/M90 rather than settle for an SC14?

 

I have headers on the motor at the moment running through a 2.5'' exhaust to the back, how exactly does the intercooling system work? Does it cool the air or the supercharger itself?

 

As for the CARTECH blow through kits, the only ones I can find are all sold and the original website (jimcookracing) seems to be shut down. Do you have a link to this setup? I'm prepared to build things from scratch as it's cheaper that way!

[nizm0zed]

http://www.ebay.com.au/itm/MERCEDES-w203-c230-230-Genuine-Supercharger-super-charger-OEM-/180745171300?pt=Motors_Car_Truck_Parts_Accessories&hash=item2a15407164

Thats a pretty common price for a M62, ex merc unit. Ebay UK and USA are a good source, UK more so. Remember to factor shipping and conversion costs.

Upto around $700 seems common.

While the Toyota charger will work fine, if its in your budget to buy an Eaton charger, its worth the extra money.

I have an Eaton M62 sitting waiting for a project, however i was lucky and picked it up for a steal, right place, right time.

 

As for the dellortos, couldn't tell you, you'd need to speak to a carbie specialist mechanic.

But, in a nutshell, you need solid floats in the fuel bowls, bigger jets, and get them re-kitted so there are no airleaks around shafts ect.

(IIRC the solid floats are called Nitrile??)

 

The intercooling works the same as a turbo system, the air goes in the supercharger, gets compressed/heated, goes through an intercooler, then into the carbies/inlet manifold.

When fuel changes from a liquid to a vapor it absorbs some of the ambient heat out of the air, lowering the temp, basically acting a bit like an intercooler.

Provided you dont try to run large amounts of boost (like a turbo) and have good ignition control, you should be able to avoid detonation quite well.

Pressure is pressure, regardless of being from a turbo or supercharger, the physical engine will handle it all the same way, same goes for the fuel/ignition tuning.

The big difference is in the exhaust restriction.

The turbo creates a restriction and lots of back pressure between the cylinder and the turbine, leading to higher cylinder temps and risking detonation sooner.

The same can happen with a supercharged engine by not having it flow well enough.

Say your engine pumps 5 litres of air (numbers out my bunghole) and is designed to flow that out the exhaust ports and onwards at around 80% efficiency

The supercharger adds another 5 litres of air at 10spi, so now your trying to flow twice the volume through the same pipe. Only flowing at 50% efficiency.

the back pressure and restriction causes higher cylinder pressures and temperatures.

Make the pipework out bigger so you get back to around 80% flow efficiency and you drop the cylinder pressures/temp but still flow the same amount of volume.

Think of it like trying to blow through a straw, you can only flow so much.

Change to a bigger straw, and you can flow more air with a lot less resistance or pressure.

[bullzed]

Thanks heaps for the information Alan, really really appreciate it. As soon as I flog my 260z, I'll be looking at this setup. Last question, do the eaton's run on a clutch system? Can they be toggled on and off at will?

 

I'll enquire around some local shops some time after christmas as to the work being done on the dellortos and hopefully I'll update my build thread with a story of success!

[zzzzed]

I had a sc14 on a datsun 1200 with an injected a15. It went like stink but was extremely noisy sounded like I had 2 engines under the bonnet. But the good part was it was switchable so I could turn it off. I got pulled over by a cop I told him it was the airconditioner compressor and he believed me because it had a similar pulley on the front

[MaygZ]

Have a read of this article.  You may find it very rewarding. 

 

http://www.fefcholden.org.au/techinfo/supercharge/norman7.html

 

Unless I read it wrong, you would be better to go back to SU's.  Selling your triples would then pay for the SC-14.  Food for thought.

 

MaygZ

[nizm0zed]

no worries zac.

 

A few of the merc chargers run on a clutch setup, not as common though.

there is an advantage to switching the charger off, the SC chargers from factory dont engage untill after around 1400rpm IIRC. they also disengage for coasting and deceleration.

This is to aid in better fuel economy and reduced engine loading.

Many other superchargers accomplish the same thing by using an air bypass system, basically bypassing out of the outlet (pressurised) back into the inlet of the charger.

There is still a small load on the engine from turning the charger like this but its pretty much non existant.

One could argue that the same power required to turn the charger with the bypass open would be the same amount of extra power the alternator takes to keep the electromagnetic clutch engaged.

It would probably also be comparable to increasing the power to weight ratio by not eating several big mac meals

One thing to be aware of though, if you are constantly engaging the clutch at higher rpm you risk desroying the clutch on the charger, but from my knowledge of it, it takes a LOT to trash one.

 

and yea, the noise.......

I had a SC12 on a gemini way back in the day, the charger was louder than the motor!!!

[bullzed]

I've looked for videos of the SC chargers and yeeeaaahhhh they sound pretty ridiculous. But if I were to rig up the SC to be turned on and off with a button from inside, and if I were to just engage it at idle, that wouldn't put too much load on the clutch I would imagine. This is only going to be used every now and again, for either track nights or short blats when I'm feeling lucky 

 

For the sake of simplicity I'm thinking about going with the SC14 because of the clutch, I realise they're less efficient but they're also much easier to pass off as an air compressor than an Eaton with the bypass.

 

I'm quite new to all of the forced induction mechanics so I thought I'd start simple, they hold their value if they're kept functional so if I get it set up and want to change chargers it shouldn't be too hard.

 

Thanks for the link MaygZ! I'm not so much going for top performance but rather just something different that gives a little bit more boot at lower revs.

 

EDIT:

 

Just have a few more questions. For one, how do you set up the air flow. Say I wanted to run the car without the supercharger engaged, if I only have intake running through the supercharger, would the turbines not get in the way and cause crap air flow? Does this mean you need two intakes?

 

And the other question I have is about the wiring. Does a supercharger need to be run through an ECU? Or can it be a simple on and off setup?

 

Also are these the floats you were talking about? Nitrophyl? http://www.rogerscorp.com/ec/producttypes/4/NITROPHYL-Floats.aspx

[nizm0zed]

bear in mind that if your going to keep the carbies, you need to tune it for boost conditions.

That means when the charger is off it'll still be tuned for boost conditions and run really rich.

If you want to set it up for occasional use, then you would be best off with programmable EFI as well, but then your adding on another $4-5K easy on top. If that doesnt scare you, then buy a nice pair of shoes as you walk down the long and expensive path....

As for wiring the charger clutch, its 1 wire, power into and grounds through its own body, very easy.

 

When the supercharger is off, you use an air bypass around it, basically like a throttle butterfly that connects the inlet and outlet pipe together.

Air will take the easiest path through, so through the bypass, not the charger.

 

Those floats are the ones i was thinking of.

I know there are companies (probably that one) that make them off the shelf for Weber carbs, should be a similar story for the dellortos.

 

your other option is a suck through setup.

This may be easier for you?

Basically you'd sell your dellortos and buy a BIG single carb, 350 holley ect.

The air goes in the carb, becomes air/fuel, goes through the supercharger, into the motor and on.

Basically the same in principle except there is no chance of an intercooler at all, the only way to manage excessive temps is lower boost, better flow and water injection.

The advantages come in the simplicity of it.

You dont need to modify a carbie for boost, you dont need to raise your fuel pressure, pipework can be very simple and short.

The charger needs to be running 100% of the time though and the fuel tends to eat away at the teflon lining over time.

 

Oh, a side thought, any cop that beleives the supercharger is aircon would probably also beleive its a turbomatic discombobulator or factory fitted damperlator.

On the other side of that, if you get a cop who does know what it is and you try and pull a fast one on him saying its aircon, you increase your chances of getting defected massively.

[d3c0y]

Sounds like you should put a turbo on it. When you dont want to use it dont put your foot all the way to the floor. Easier to tune it of off boost situations too. Also dont you think a supercharger designed for a 2L engine might be a bit small?

[Ben]

You'll spend more time and money trying to get it to run properly than actually driving it (which is a non-sensical statement, but you get the idea...)

The SC14 was from the 1G-GZE 2L, and there are many better options available these days. Heed those who have suggested even the 'old' M90 as a more viable path. And _please_ convert to EFI, the carburettors will give you nothing but an empty pocket.

[MaygZ]

And the other question I have is about the wiring. Does a supercharger need to be run through an ECU? Or can it be a simple on and off setup?

 

I'm a little confused here    How or why would you be running an ECU with triples?

 

I agree that without any doubt at all, the set up that you seek would be far simpler and more reliable with EFI than carbies.  Then a programable ECU would almost be a necessity.

 

MaygZ