Twin Charger....hmmmm

[Boxersix]

Originally Posted by TomsSVX

Just need that Hydra to get started here

Tom

Hey, I'm working on it. I don't quite have ~$3K in the budget right now to buy a digital four channel osciliscope right now. The person who said they had one and would allow me to get the info I need flaked out. Weaksauce....

I need it just as bad as you

[TomsSVX]

Originally Posted by Boxersix

Hey, I'm working on it. I don't quite have ~$3K in the budget right now to buy a digital four channel osciliscope right now. The person who said they had one and would allow me to get the info I need flaked out. Weaksauce....

I need it just as bad as you

Ouch O-scopes are teh Expensive!!!... No rush either, I am still absorbing the costs of setting up my shop and am burrying myself in work to try and pay the bills... so I feel your pain. I do need to ask again, what the expected price tag is and it will be plug and play correct?

Tom

[svxistentialist]

Originally Posted by TomsSVX

Ok here are the maps I am working with. Doing the math in a perfect world I would expect 39psi using a pressure ratio of 2.5 on the turbo and the 1.8 I see now on the supercharger. Now granted there will be pressure lost in the real world this is just a round about. Maps for both compressors are below. The lysholm graph is a PDF attached at the bottom
Tom

How come our maths are not adding up here Tom? Am I missing something or taking too simplistic a view?
My derivation looked only at the pressures before and after each of the pumps in series. In my sums, the turbo yields 2:1 on atmospheric, followed by the PD blower raising that ante by 1.8:1. That gave 39lbs boost over atm
Yours has 2.5:1 followed by 1.8:1 giving 39 lbs. Can't both be correct.

Originally Posted by TomsSVX

fully understood Joe, thats why I mention a perfect world scenario. I am still on the fence of before or after s/c injection.

tom

I now see why you would. Move up on the fence, I want to get on.
Detonation control it must be. What you will have to use as overall control is how well you can cool what the turbo is pumping into the blower.

Originally Posted by Boxersix

your answer lies in what you mainly intend the injection TO do......cool the charge or control detonation. It obviously can and does do both but where you plumb it and how you tune the injection will determine the end result.....

I think lads because of the difficulty of dumping all that compression created heat from both chargers it will not be necessary to run at [very] high boost with the turbo, otherwise cooling effectively before the blower will not be optimum.

If my figuring is correct [please correct me if you see an error in my thinking] running the turbo at a pressure ratio of 1.7 followed by the blower at the same 1.7 will theoretically yield 14.7 x 1.7 = 24.99. 24.99 x 1.7 = 42.5 psi absolute pressure.
Subtract 14.7 from this gives a boost figure of 27.8 psi. This figure of around 2 atm is theoretical only, as the lysholm won't hold it. SFAIK it will leak-back at high pressure.

[sicksubie]

the blowers cannot run at 1.7bar though. Not even 1 bar

[svxistentialist]

If my figuring is correct [please correct me if you see an error in my thinking] running the turbo at a pressure ratio of 1.7 followed by the blower at the same 1.7 will theoretically yield 14.7 x 1.7 = 24.99. 24.99 x 1.7 = 42.5 psi absolute pressure.
Subtract 14.7 from this gives a boost figure of 27.8 psi. This figure of around 2 atm is theoretical only, as the lysholm won't hold it. SFAIK it will leak-back at high pressure.

Apologies chaps. Disregard the last paragraph. Quite literally I forgot about joined-up thinking

The 1600AX WILL work in this configuration of course. It is boosting from 25lbs at intake to 43 lbs output, so the pressure delivered is only 18 lbs, and leak-back does not apply.

However, I have run another set of figures and they are far more relevant. The absolute restriction on what this system can produce in this configuration, turbo followed by blower, is determined by the max airflow the blower can pass, the afforementioned 702 CFM.

Taking this figure as the max charge we can force in there, and given the EG33 parameters that we are feeding, the approx max hp we can make in this setup using best possible intercooling is 455 hp at crank and the pressure required to achieve it is 18.5 psi.

Because this is a limiting factor it's both good and bad news.

The bad news is that we can't expect to yield any more from this blower, no matter what size turbo you pair it with because of the 402 CFM limit.

The good news is we can run both chargers at low stress levels, and be better able to manage the heat produced to give us 455 hp.

By my estimates you need a turbo supplying 1.4 pressure ratio [~=6lbs] followed by the blower giving 1.6 pressure ratio, ~ 9 psi. This should give a combined total of around 18.5 psi with airflow of 700 CFM.

That's all the blower can deliver, but it's 455 hp if properly cooled.

Joe

[Tim]

Originally Posted by Boxersix

Hey, I'm working on it. I don't quite have ~$3K in the budget right now to buy a digital four channel osciliscope right now. The person who said they had one and would allow me to get the info I need flaked out. Weaksauce....

I need it just as bad as you

I think my dad has a regular osciliscope... will that suffice?

[TomsSVX]

Joe, where are you finding the max cfm's for the blower?? I have been digging on Lysholm's site for some time now with no results

Tom

[Dessertrunner]

You are all talking CFM, isn't it correct that the CFM of the SC is inrelationship to the boast. In simple terms 15 pound boast has twice the air at the same CFM? The capacity of the SC is based on a given CFM @ a agreed infeed pressure and out feed pressure. In simple terms double the infeed pressure give twice the amount of air but with the same revs of the SC.
Tony

[TomsSVX]

Thats what I was thinking of as well, but I am sure there is a limit. The max CFM but at what pressure. Joe don't forget, you can pack plenty of pressure into one cubic foot

Tom

[svxistentialist]

Originally Posted by sicksubie

the blowers cannot run at 1.7bar though. Not even 1 bar

Difference in convention here

When people say 1.7 bar boost, they usually mean adding 1.7 bars pressure to ambient or atmospheric.

That is not what is implied here by the term pressure ratio.

What it means in this context is we are adding 0.7 bar to 1 atmosphere when dealing with ambient.

What it means when pumping out of a pressurised [over atmospheric] plenum is you multiply the "before" pressure by this factor to get the "after" pressure.

Joe

[TomsSVX]

to put it simply, your engine N/A runs on 1bar of pressure. With the blower running at 1.8 on the smaller pulley, you are adding .8bar or 9psi... (that probably complicates it more though)

Tom

[TomsSVX]

Originally Posted by svxistentialist

How come our maths are not adding up here Tom? Am I missing something or taking too simplistic a view?
My derivation looked only at the pressures before and after each of the pumps in series. In my sums, the turbo yields 2:1 on atmospheric, followed by the PD blower raising that ante by 1.8:1. That gave 39lbs boost over atm
Yours has 2.5:1 followed by 1.8:1 giving 39 lbs. Can't both be correct.

The turbo running at 2.5

14.7*2.5=36.75

36.75-14.7= 22.05

S/C running at 1.8

22.05*1.8= 39.69

Now I may have been doing the math wrong so lets try it a different way

14.7*2=29.4

29.4*1.8=52.92

52.92-14.7=38.22

Although I thought for a minute that subtracting ambient before the s/c may be right you are probably correct in subracting it after both

Tom

[svxistentialist]

Yeah, that second one is the same way I did it Tom. You only subtract atm at the end, and only once. It was using the concept of absolute pressure as mentioned in Nevin's article.

Joe

[svxistentialist]

Originally Posted by TomsSVX

Joe, where are you finding the max cfm's for the blower?? I have been digging on Lysholm's site for some time now with no results

Tom

Originally Posted by TomsSVX

Thats what I was thinking of as well, but I am sure there is a limit. The max CFM but at what pressure. Joe don't forget, you can pack plenty of pressure into one cubic foot

Tom

Tom, Tony, I'm using a spreadsheet that calculates the figures based on known parameters for the blowers. Graham developed it.

Tony, the CFM for the blower is calculated same as the CFM for the engine, and is basically limited by the swept volume and the max revs and the efficiency ratio. This defines the maximum volume of air the blower can pump.

Essentially the flat six also is a pump in this context.

Tom, the CFM for the Lysholm is a derived figure. Here is how it is calculated:

Blower Cubic Inch Displacement x Max Continuous RPM x Blower Efficiency Ratio all divided by 1728 to convert from a cubic inch figure to cubic feet.

And so: 97.63792 x 13,500 x 0.92 / 1728 = 702 CFM

Joe

[TomsSVX]

to be honest, if this is indeed the case it would not be worth while. I am having a hard time wrapping my head around that though. I can see that being the case at atmospheric pressure.

Tom