8v 2l Twin Charged -my Little Project

[slyalfa]

the turbo feeded a roots has been done many times turbo mag did one a while back where they put v6 into a mr2 and did a turbo feeding the roots. it seems to work out very well.
the turbo blowing into the roots seems to negates any drag. they had the roots going right in no intercooler. but the turbo did. using a large turbo was not a problem as the roots get the boost at idel and up to about 1/2 way. the boosted motor then is making more power at the getgo so there is a lot of flow to spin up the turbo. so the turbo come up much much sooner.

the roots will not spin any faster then it would with out any turbo so overspeed is not a problem.
as for heat when it is not doing any work there is not noticable heat made. in fact it is cooled if anything. if the IC on the turbo is working. but it has to be a roots type if it is the Lysholm type it will not work. as it will recompress no mater what. the roots type do not use a clutch as the drag can go vely low in bypass mode. but the Lysholm has a lot of drag nomater what so they normly use a clutch like the AC has on them.

[buzzed]

I agree VW predominantly did it the way they did for fuel acconomy
Integralli - interesting, I looked at the engine layout and it appeared to be that they pressurise the supercharger inlet and then bypass. There is certainlya bypass on the charger, but perhaps this is only for blow off when off the power.

OK, I am with you now. I follow where you are coming from.

I suppose I need to wiegh up the pros/cons of continuing to spin the charger and the impact on intake temps given the lack of second stage intercooling. Perhaps with meth water injection, I might still be able to run 10psi from the charger without completly unacceptable intake temps (15psi from turbo intercooled, 10psi from s.chrgr without intercooling). I'd be able to run less boost from the turbo at that point, allowing for a turbocharger size reduction and consequent in rotating asm inertia.

Yeah the more I think about it, the more I reckon you are right, hmmmm. BTW, I printed off you infor from your webpage, bit of good reading one of these nights.

5yrplan - I agree in regard to the buffer manuifacturers must run on tunes in order to ensure minimum claim costs on vehicles. I mean for example, take shell 100 octane. Min octane is 100. People run out to the nearest dyno tune on the fuel to within an inch of detonation onset, then wonder why the engine pops 6months later with the same fuel. The octane on this fuel is min 100, it can often be 103...what happens if you tune to 103 then then next batch is bang on 100?.......So many things to consider. On that point, my past builds have always run a knock sensor...saved my engine a couple of times.

Guys thanks heaps for your time and thoughts, greatly appreciated. One thing is for sure, I WILL have this system running...hopefully before the year is out.

cheers
Mike

[Greg Gordon]

The bypass on the Delta S4 is somewhat deceiving. It looks like it bypasses the supercharger, but it actually bypasses turbo and supercharger pressure back to the intake system.

The Delta S4 also has two intercoolers, one after the turbo, and one after the supercharger. I think that's the way to go if you can find the room. If not, I am sure you will be fine if you add a good water injection system. Don't underestimate the anti-knock protection from water injection. It's FAR more powerful than any intercooler in that regard. I can put up a chart with NACA data to back that up if I need to.

Greg

[alfatwincam]

Quote:

Originally Posted by Biba69 buzzed, you mentioned making your own monoblock. My guess unless you have a great computerized milling machine it might take a bit of time. I exchanged a few emails with the fellow (can't think of his name right now) who makes them in Australia. Some years ago I also exchanged a number of emails with Jim Steck (in the US) and I mentioned this monoblock since Jim was in the process of making his own for the Bonneville TS. Jim felt there were inherent flaws in the Australian design and designed his as a combination of girdle and monoblock. Jim sent me the first photo after 12 hours of straight milling. The second is of the competed work of art. Biba

[Alleggerita]

I would still say twinspark all the way - they have a stronger/reinforced block among other things - given that you seem to have one in the garage ....

There are some guys that change the optics of the head. See
motorenbau
Now you just need a custom casting for the valve cover that mimics the old GTA/m and fits on that head and it will look way cool

[5yearplan]

Quote:

Originally Posted by Greg Gordon The bypass on the Delta S4 is somewhat deceiving. It looks like it bypasses the supercharger, but it actually bypasses turbo and supercharger pressure back to the intake system. The Delta S4 also has two intercoolers, one after the turbo, and one after the supercharger. I think that's the way to go if you can find the room. If not, I am sure you will be fine if you add a good water injection system. Don't underestimate the anti-knock protection from water injection. It's FAR more powerful than any intercooler in that regard. I can put up a chart with NACA data to back that up if I need to. Greg

[Greg Gordon]

Delta S4 Diagram,

Sometimes I think I have a diagram or chart for about everything supercharged...

[5yearplan]

oh, okay, so when the BOV is engaged, the charged air is sent back to the inlet for the turbo, right?

[Greg Gordon]

Exactly. When the valve is open ALL charge air goes back the the intake system. It's actually a bypass valve, a blow off valve would dump it into the atmosphere.

I used an identical bypass system on my Grey supercharged GTV6.

Greg

[buzzed]

On the s4 diagram, theres a BOV that dumps all boost back to intake, but the thing that is throwing me, is there is also a bypass around the supercharger, allowing turbo pressure to bypass the s/charger. For this not to be a staged system, it would mean that the s/charger bypass would open at the same time the BOV opens, which makes no sense to me.

Greg, teach me ;-)

As for the casting of the twinspark cover...gee you guys sure do know how to make my project bigger than everest...haha...I had thought of it though thats for sure. Thats interesting that you say the twinspark block is reinforced, I had not noticed that outwardly, how so?

Link works for me. But German is not my strong point, what is meant by changing the optics of the head?

Heres a pic of the VW golf setup and a real world photo of the lancia s4 rear end.

[Greg Gordon]

I should clarify a few things here. I have not built a compound system like this. I have built a few engines with single superchargers. Everything I know about compound forced induction is from my fairly extensive library on forced induction. I wouldn't write anything I wasn't darn sure of, but it's always possible I am missing something.

I have never seen a Lancia Delta S4 or any other Lancia Delta for that matter. However in the technical drawings I have there is no visable bypass around the supercharger.

I strongly suspect if we get a closer look at one we will find that the throttle plate or plates are downstream from the supercharger. During upshifts when the throttle closes a massive amount of air needs to be dumped out of the discharge pipes or pressure will quickly spike high enough to blow off couplers, wreck the supercharger bearings, bend the throttle plates or worse. The pressure spikes because when you close the throttle the turbo and the supercharger are still pumping air, but it doesn't have anywhere to go. I have personally seen spikes above 100PSI during upshifts with a bypass valve failure!

I generally avoid commenting on odd German designs because these odd ideas usually die rather quickly. They really do some weird stuff. Having a turbo between a Roots blower and the intake manifold is just plain weird. Then again, so is installing a supercharger at a 90deg angle to the crank shaft and driving it with bevel gears. Yet, they did that. They also drove a centrifugal with a hydraulic variable speed transmission like a Buick Dynaflow. At one point, not long ago they tried to bring the scroll-type supercharger back from the dead. Let's see if this new twin charger design lasts as long as these other ideas.

Greg

[5yearplan]

It looks to me that the bypass valve merely represents the superchargers wastegate, as opposed to implying that the supercharger is purposely bypassed. It seems both inefficient and unnecessarily overcomplicated to try to develop a reliable/useful way to bypass the SC and run off of the turbo alone. But you never know...

[ToonRboy]

Hey Buzzed,

Nice Alfetta. Ambitious plan. I like it & I hope you "git 'er done!" ;p

I understand what you're attempting to achieve with regard to the challenges to overcome with turbo lag and target HP. Especially when starting out with just 2L. Naturally, if you have a bullet-proof engine, you can get your taget HP (and more) with 1.5L. Problem is the open block design. Very difficult to seal those kind of combustion pressures when you exceed stock output by well over 100%. Not to mention component failures.

Anyhow, since it's been done (and documented) there's not much to argue. However, I'd like to make a few points.

Quote:

I plan to pressurise the supercharger inlet with the turbo charger.

[buzzed]

Hi ToonRBoy,

Thanks for taking a look at my slightly crazy conversion :-)

I have to disagree with you on a few points though..

Rotary like a 2 stroke....Nope I'm afraid not, it's a 4 stroke. My numbers were not calculated for the rotary anyway, that was meerly eye candy showing a past project :-). Besides, you assume because I have built a rotary that I don't work on 4 stoke piston engines. I do, In fact I have sized many turbos for people and am quite accurate at predicting lag, torque and power outputs at particular boosts, including but not limited to my latest project, a 6cyl RB25 DE, with turbo setup, 8:1 comp, forged internals, 400hp, and bugger all lag. I know how to size a turbo ;-).

In fact on the rotary I ran a GT3540, as apposed to the GT3071R I plan to run on this setup. The nissan motor also runs a GT3071R....but of course it has higher mass flow and therefore lag is less of an issue at this sizing and we can also get away with a couple less psi and a few more rpm.

Probably the missunderstanding here is that I am quoting flywheel, real hp....not rubbish power figures that are run on the dyno at the wheels and then multiplied by a factor inversly proportionate to the users old fella. I get tired of magazines unknowingly publishing peoples imaginary hp figures...but thats a another story.

Bottom line, on a 2L 8v single spark Alfa motor, she will need 25+psi to get 400 true engine hp on pump fuel at 7300ish rpm.

As for graphs of Turbos showing rpm...