[Ecotec] Factory L67 TwinCharged Plans

[warrjon]

this is a good read guys ok luke from what i understand [ im new to turbos]you want a large zorst housing on the turbo but not to large on the intake side as it is not realy needed. is this right. just big enouf to make the low amount of boost you need but the rear needs to be big simply not to be so much of a restriction. so in this application would a rear housing of 1.20 an front of say .55 be right what your after ????

It is actually the other way around in F1 they used very large compressor housings and smaller turbine with very large wastegates. The large wastegate flowed enough to make extreme HP with the TC spooling very quickly.

here are pictures of the old Ferrari and Renault turbo engine of the 1980's, they have a very small turbine housing

 

[Matt_vp]

Are those f1 motors super and turbo charged? I think eaton v8 was talking about a turbo super charged v6.
Matt

 

[eaton v8]

yea i was talking about this thred mat, this thred just got me thinking. and after a big shed clean up i found sertain parts laying around........ but anyway was i on the right train of thought.

 

[VN_Luke]

this is a good read guys ok luke from what i understand [ im new to turbos]you want a large zorst housing on the turbo but not to large on the intake side as it is not realy needed. is this right. just big enouf to make the low amount of boost you need but the rear needs to be big simply not to be so much of a restriction. so in this application would a rear housing of 1.20 an front of say .55 be right what your after ????

Hey man,

Yep that's my theory in a nutshell - whether it's actually correct or not... is another story all together - I'm always open to opinions/other theories.

The above two F1 engines are 1.5 litre v6's (i think?) - that rev to like 13,000rpm and ran (up to 4 bar boost). - notice that they are both also twin turbo setups (i.e. one turbo for each 3 cylinders).

These engines also ran on different fuel to what comes out of our pumps, which would allow a lot more ignition timing despite the added exhaust pressure (although a big gate will help relieve that pressure, no doubt).

in a turbo-only application a smaller exhaust housing will give great response, but there'll be more top end power to be made with a less restrictive exhaust. - Which way you go depends what your car is designed and built for.

My theory is that on a X litre engine with a supercharger running, you have the same amount of exhaust gasses as a larger motor - for pure example's sake, let's say you have a 3 litre motor, running 10 psi from a supercharger. This would say ... produce the same amount of exhaust gas as a 5 litre motor.

Now my theory is that you size the exhaust housing more to suit a 5 litre motor than a 3 litre motor as it should spool just as quick as it would on the bigger engine, while providing a free-er flowing path for the exhaust up top.

On the intake side of things, however - the compressor only needs to fill the 3 litre engine with air, and (if you keep the supercharger turning all the way) it's very easy to reach your desired boost level because the supercharger's compounding effect.

I'd also edge towards running as little boost from the supercharger as possible and using the turbo to generate most of the boost up top as it would be more efficient if you want to make big power.

A Large wastegate is also highly recommended in my books

Of course as I said before, it's all a fine balance of when everything happens - and the only real way to know what will work on your combo is to try it - I could be completely off the mark, and would love to see results from people that have tried other ideas!!

here's some great relevant info anyways: Engine & fuel engineering - twincharging estimated results

 

[eaton v8]

well from what i found out when i was thinking about putting this turbo on the ute [5l] and that it would spool early on maybe as early as 2g but run out being efficiency by about 5 to 6g so if the thery is correct and a l67 pushes about the same amount of air as a 5l this should work well. i might go and dig around the back of the shed and see if i can dig up a l67 somewhere or it might just be a squeekoteck but i think i have one laying around somewhere just collecting dust. i had ideas for a boat anchor once.

 

[eaton v8]

gee you fin some good material to read luke its very helpfull

 

[warrjon]

The above two F1 engines are 1.5 litre v6's (i think?) - that rev to like 13,000rpm and ran (up to 4 bar boost). - notice that they are both also twin turbo setups (i.e. one turbo for each 3 cylinders).

These engines also ran on different fuel to what comes out of our pumps, which would allow a lot more ignition timing despite the added exhaust pressure (although a big gate will help relieve that pressure, no doubt).

Sorry folks I did not really explain myself properly the point was exhaust turbine housing size in relation to engine HP, turbo spool and exhaust gas flow capability.

in a turbo-only application a smaller exhaust housing will give great response, but there'll be more top end power to be made with a less restrictive exhaust. - Which way you go depends what your car is designed and built for.

These F1 engines made 1000hp and reved to 13000RPM with a very small turbine housing.

Engine HP is directly related to air volume CFM regardless of engine capacity.. What I was trying to explain was...

Lets take an extreme scenario.... a very large compressor housing say a Garrett T76 rated at 700hp so this compressor can flow enough air to make 700hp regardless of turbine housing size.

The turbine housing will govern how quickly the TC spools..... so lets take another extreme scenario with the T76 compressor connected to a very small turbine AR say a 50AR this TC will spool very quickly but run out of flow at the top end because of exhaust back pressure.

Now if we add a large enough Wastegate to the 50AR TC so it can bypass the flow it does not matter if the flow goes through the TC housing or wastegate so your free flow path will be via the wastegate. This should give extremely fast TC response with the ability to flow exhaust gas at high RPM.

This is what I am planning to trial so as soon as I can gather all of the bits will start the R&D

 

[warrjon]

Now my theory is that you size the exhaust housing more to suit a 5 litre motor than a 3 litre motor as it should spool just as quick as it would on the bigger engine, while providing a free-er flowing path for the exhaust up top.

On the intake side of things, however - the compressor only needs to fill the 3 litre engine with air, and (if you keep the supercharger turning all the way) it's very easy to reach your desired boost level because the supercharger's compounding effect.

Oops hit the submit button dam glide pads

It does not matter what the capacity of the engine be it 5L or 1.5L if it makes 500hp it will consume 750CFM of air on the inlet side and this air needs to exit so exhaust gas flow will be the same as well.

As an example if you have a small turbine with a 57mm exducer and a 60mm wastegate gives a total Xsectional area of 5467mm and a larger 84AR turbo with a 73mm exducer and 35mm wastregate total area is 5145 so larger TC will flow less total exhaust gas

As I mentioned before it does not matter whether the exhaust goes through the TC or wasegate as long as it can exit for the desired HP rating

 

[HoldenManDan]

here's some great relevant info anyways: Engine & fuel engineering - twincharging estimated results

Man i just read that whole thread, what a great find and an equally good read!

I'm glad so much of it made sense to me, kinda lessened the confusion about the topic! Anyone that hasnt read it, should!

I know it's been changed around a few times, but essentially it'd be agreeable to only have the one IC for numerous good reasons. Now which would be better: intake>turbo>cooler>supercharger inlet>intake manifold, or intake>turbo>supercharger inlet>cooler>intake manifold, eg on an m90 equipped car, the piping runs like this (not a commo i know but shows the piping well):

I'd be leaning towards the first option though, having the cooled air from the TC then IC entering the supercharger inlet to be boosted again, then into the engine.

Just thinking about this from a layout point of view also. I originally planned to go turbo only after running the M90 for a while. I've always liked the idea of having the turbo off to one side, preferably on the passenger side of the motor as opposed to right in front of it. This is for both looks and accessibility to parts of the front of the motor. I understand it may be better in terms of functionality to have the turbo right in front of the motor, as it's more likely the turbo would be receiving exhaust gases from both banks more simultaneously than if it were off to the side. The decision made here will obviously also determine the way pipes are run both to and from the turbo and cooler, then to the s/c inlet.

I'd like to hear people's thoughts/experiences with either or both setups and what they think would be better.

I know it might seem like the layout isnt what should be worried about so much at this stage, but i feel like if i've got the layout down pat then i've made a start!

As for turbo sizing, Commotion recommended me either a t04z or gt4094, but that was to run turbo-only. Thoughts? I'm not really up to speed on turbos at all to be honest, but would gladly be shown the way!

Cheers

 

[VN_Luke]

Oops hit the submit button dam glide pads

It does not matter what the capacity of the engine be it 5L or 1.5L if it makes 500hp it will consume 750CFM of air on the inlet side and this air needs to exit so exhaust gas flow will be the same as well.

As I mentioned before it does not matter whether the exhaust goes through the TC or wasegate as long as it can exit for the desired HP rating

I agree with both points - I just figured that the small housings are used so that when the 1.5 litre is *not* making big power, the turbo can still have razor sharp response. - whereas with a larger motor (or a supercharged small motor 'emulating' a larger motor) this same kind of response can be had with a larger housing.

as for top end flow, I see how the gasses can flow either through the wastegate or the turbo - Although wouldn't it be more efficient to let them flow through the housing?

I read somewhere that the compressor needs a certain amount of energy to make it produce boost in the intake.

so now lets say you have two of the same sized compressors, and a huge and tiny rear for them both... they both need the same (or close enough) amount of energy extracted from the exhaust gasses to achieve the boost we want on the compressor side.

Now I read that smaller exhaust housing will require the exhaust gas to be under more pressure in order to extract the same amount of energy as a larger housing would, with less pressure.

I.e. larger housing allows more flow, so less pressure in the exhaust required to get the same amount of energy through, and vice-versa. - having said this, the more pre-turbo pressure the quicker the spool up, and the more mass flow through the turbo, the more potential energy can be extracted to drive the compressor.

Hopefully I'm making some kind of sense so far - ...

ok, since the wastegate is controlled by the *intake* side of the engine, it will set the exhaust pressure to whatever it needs to be in order to maintain the desired boost level on the intake, regardless of how big the gate is. (although of course if your gate is too small to vent all the 'waste' exhaust gas, boost creep will ensue)

Some pressure in the exhaust is fine - but in my opinion too much pressure will cost power and lead to a 'more dangerous/closer to detonation threshold' running engine.

So applying the above ^^ theory to the example you have given with the T76:

- The .5 AR rear would require more pressure in the exhaust manifold than a 1.0 AR rear in order to make the same amount of boost. - Regardless of how big the gate is.

- The 1.0 AR would spool later than the 0.5 AR, due to the lack of exhaust pressure excerting torque on the turbine wheel.

- The 1.0 AR can potentially harness more energy to drive the compressor.


Another thing to note would be exhaust flow - most tubular turbo manifolds have a nice merge collector going into the turbo exhaust inlet - the gate is at an angle etc and doesn't lend itsself to good flow (although usually the exhaust is under pressure anyway so this doesn't effect boost control) - I have seen some interesting setups running a wastegate OFF the actual turbine housing! - I'm beginning to see why!


At the end of the day - it's a work of art to balance all these things nicely, to create an engine that suits it's intended purpose as best it can!- and therein lies all the fun!

I presume your approach, warrjon, is to drive the supercharger at a decent overdrive ratio, and as such, the turbo won't have to work very hard in order to achieve the total required boost once compounded? - If this is the case, a small rear housing would work nicely, as you won't need to extract much energy to drive the compressor, and hence the exhaust pressure won't need to be very high.

I would imagine this kind of setup will produce very quick full boost, and give a very flat torque curve throughout the rev range, however, at the sacrifice of sheer top end power... but regardless, this would make an awesome street car!

I've gone with the approach of having the supercharger cranked right up for great and responsive low end, and to spool a turbo with a big exhaust housing quickly. Once the turbo gets happy, I switch off the charger, and let the fully spooled turbo with it's big exhaust housing take care of business up the top. The idea is to use each method of forced induction at the point where it works most efficiently - and take full advantage of them both.... while somehow switching gracefully between them somewhere in the middle - but i do intend on experimenting with a few things which might make me change my approach!

^ Anyway, wow, what an essay! I might have gotten a bit carried away with that post.