Twin Charger....hmmmm

[TomsSVX]

well the seed was planted and I am having no luck moving this stage 3 so here's an idea.... Keep the stage 3 supercharger running on a Hydra or other standalone. water/methanol injection. AND a single garret gt40 series tubo... I thought I was going to use the 4088r for a large single turbo but if I am tiwn charging I can use something a little larger as there is not as much lag. It was suggested to use a 4094 as per my original intentions that were changed from the turbo setup I had wanted to do.

So after the VERY confusing statement, I ask.... Is twin charging going to be worth it?? Also, how much of the turbo am I going to be losing through the PD blower... BTW the turbo will feed the s/c.

Tom

[Trevor]

Originally Posted by TomsSVX

So after the VERY confusing statement, I ask.... Is twin charging going to be worth it?? Also, how much of the turbo am I going to be losing through the PD blower... BTW the turbo will feed the s/c.

Tom

I would expect that you will have to run the SC at much higher RPM than usual, in order that it will boost a high input pressure. It has as it were, to catch up on an already fast moving air stream and push it along some more.

Worth it? You have had a guts full with the SC, and did not really sort it so is adding to the complexity involved going to drive you up the wall???????? Frankly on several counts, no IMHO.

[It's Just Eric]

I think going twin charged would be cool, but you run into a problem:

Your already pulling timing, presumably because the intake charge is HOT. twin charging would best be donw with a centrifugal supercharger and a turbo, both being run through an intercooler

if your "stuck" with the stage 3, it might be wise to cool down that intake charge and run a standalone ems. Im sure that would be key to making ANY fi system on the svx work

[TomsSVX]

Originally Posted by Trevor

I would expect that you will have to run the SC at much higher RPM than usual, in order that it will boost a high input pressure. It has as it were, to catch up on an already fast moving air stream and push it along some more.

Worth it? You have had a guts full with the SC, and did not really sort it so is adding to the complexity involved going to drive you up the wall???????? Frankly on several counts, no IMHO.

Thanks for the reply Trevor, I had always thought it would be useless the twin charge a PD blower, But here is my questions. The PD blower is meant to move a fix amount of air at atmospheric pressure and pressurize it internally to release a fixed ratio of more pressure into the intake. Now that being said, if the inlet side of the blower has more than atmospheric pressure(from a turbo in this case) would it create the same ratio to increase air velocity?? Or would it be more of a restriction?? I hope I am making my thoughts clear.

Tom

[Boxersix]

I've built a few twin charge setups. Even worked on one of the original Lancia Delta rally cars once. The PD blowers can be used in a twin charge arrangement you just typically need to spool down the SC a little bit with a larger pulley, to keep the rotors from exceeding their flow rate by a bit rate if a large(IE 4088R). You don't want to exceed the rotors maximum airflow with the turbo you use because you'll cause massive surge at the turbocharger inducer when the flow rate of the rotors peak.

TC setups also help the bigger turbos spool a little faster as well as the volume down low the SC draws puts a low level vacuum between the turbo and SC rotors, reducing the compression force the turbo must exert during spoolup(building pressure). Once the turbo CHRA gets up to speed this vacuum is gone however most really big(GT35 size + ) you'll notice the turbo will spool up a hundred or two RPM sooner. Plus you get the low punch of the SC.

I've never had a problem using the Lysholm's either. biggest thing is to map out the turbo's flow rate at your intended useage against the flow rate of the PD blower you'll be using. I have no idea what type and size blower Mike(lan) used in those S3 setups he built.

-Adam

BTW....still working on that Hydra EMS, just slow right now trying to get some more stuff figured out I've got so much money tied up in so many areas around this project car I'm going looney....

[TomsSVX]

the lysholm is a 1600ax. I really need the answer to my quesiton above. If there is positive pressure on the inlet side of the PD blower, will I still see the same fixed amount of airflow as if there were not (atmospheric pressure)??

Tom

[RallyBob]

An excellent example of twin-charging in the real world. GT40 turbo, Eaton supercharger, Volvo engine in an old Opel Manta. 578 hp on pump gas.

http://www.hilmersson-racing.com/start.asp?show=ec

There are numerous videos here, including 1/4 mile runs and a dyno pull.

Bob

[Boxersix]

Originally Posted by TomsSVX

the lysholm is a 1600ax. I really need the answer to my quesiton above. If there is positive pressure on the inlet side of the PD blower, will I still see the same fixed amount of airflow as if there were not (atmospheric pressure)??

Tom

There's no direct mathematical formula to determine the actual flow output(as far as I've researched and worked with) as the two compressors have an infinite variable of shaft input speeds and output temps, but also how fast the turbos get up to those speeds. It has a direct correlation to the input pressure as well as the inlet air density(based on inlet temperature)..so you can see some slight fluctuations in the boost curve if you are pushing a turbo beyond it's normal efficiency range and start forcing really hot air into the screws. Hardly going to happen with a 4088R unless you're talking crazy power numbers here.

Every system is more of a trial and error in setting up and tuning but they do work, and work well once setup correctly. But overall the PD blowers don't care if the ATM is 14.7 psi or 28 psi. They just suck and compress the air. The setup just essentially creates a higher ATM than the normal 14.7 and the SC does it's work. You must intercool the crap out of the charge air pre SC as the PD blowers can really heat up the air in the upper PR levels, and adding already hot air to the mix just compounds that effect.

1200 and 1600ax are what I've used in the past with excellent results, no reason you won't have the same. I've never set up something with a 4088R and twin charge, but I've used the Turbonetics GTK550 and the Garrett 3076, 3071, and 3582 r's all with good success.

1600ax flows 1.6L of air per revolution of the female rotor(5 lobe) per positive displacement. Has a max efficient PR of about 2.0 but can carry up to 2.2 at most IIRC. Max rpm input of 1600ax I believe is about 14-15000 rpm. 14K rpm it's flowing ~ 22400 L/min worth of air. If you need the map for it let me know as I've got all the Lysholm stuff here in a file somewhere.

-Adam

[Trevor]

Originally Posted by Trevor

Worth it? You have had a guts full with the SC, and did not really sort it so is adding to the complexity involved going to drive you up the wall???????? Frankly on several counts, no IMHO.

Tom, I think your opening hmmmmmmm, says a lot.

As a commercial engineer I am aware that one should always do the sums especially including R&AD, along with design theory. I see no figures included relative to contingencies, e.g. pressure losses or in costing.

[svxistentialist]

Originally Posted by sicksubie

is the S/C limited though to an input charge of 1.4bar?

No. In theory there is no limit, only what the turbo is able to deliver.

In practice the limit of what will actually work is imposed by the practicality of how much compression heat you can remove from the compressed charge. The more bars you give it, the more heat. If you can't get the heat out, then you are not getting the oxygen in, then you won't get the horsepower.

Originally Posted by TomsSVX

whoa, a lot of text there. i just want to make sure I understand what you are saying.

W/o the twin charger an effectively cooler charge on the supercharger alone would yield 455hp if cooled and tuned properly.

That's correct. However, I have had another look at the calculations and I have a revision on this hp figure to 440. Graham is using a higher maximum pressure figure for the 1600 of 18.5 psi. Based on the chart I'm not happy with this. You Tom are using a conservative 12 lbs. This also is incorrect, too low. The usable figure is 1.8 pressure ratio, which adds [or boosts, if you prefer] 17 psi. 17 psi yields 440 hp from the EG33 at 80% intercooling efficiency.

Originally Posted by TomsSVX

On the other hand, having a turbo that is effectively cooled running at a rate of 1.4:1 and also having effective cooling for the s/c this would result in a yield of 637hp.

Tom

Yes, I believe this is correct, but needs to be adjusted as above, and is a theoretical maximum. I did mention it was a simple calculation, with no factors for inefficiencies added in, as Trevor correctly cautions. The figure of 637 above is based on the 455. Recalibrated to 440 and the more reasonable boost it should read 616 hp.

Taking into account that in a real system there will be losses you need to take account that the above calculation assumed that the pre-blower intercooling was 100% efficient and no oxygen loss, this figure has also to be calculated downwards to real-world intercooler efficiency ratios.
{This is partly the reason I kept the turbo figure low, Sicksubie, to make the intercooling work}

If you re-calculate the post turbo intercooling to be a more reasonable 80%, the oxygen multiplier factor drops from 1.4 to about 1.15, this will be equivalent to 500 hp give or take one or two.

Tom, considering your twincharger system is very, very sensitive to how much charge cooling you can pull off, you should genuinely consider adding cooling right now, using supercharger only.

Cool the hell out of it and run it up to 17 lbs, you will get 450 hp no sweat.

I like the twincharger idea though, but fabrication and efficient cooling will be your nightmare. It can work though, absolutely no doubt about that. Sorry about all the text.

Joe

[TomsSVX]

Joe I understand that fully. BUT I cannot run any more than 12psi without have a chrank pulley made the half the size of the engine. Not to mention that would be well over the efficency of the blower. I do plan on doing this in stages. Firts things first, i need to get my rod bearing replaced which has been stamped. Once that is taken care of I intend on following through with an end user programmable EM, most likely the hydra that Boxer6 is working for simplicity. Once those two things are up and running, the water/meth injection would be next to see how well this is actually working. I will have two EGT sensors and an intake temp sensor at that point as well to see what the cooling is actually doing. Once all is well with the supercharger and EMS, then I will be working on some form of a twin charger. The EMS will be tuned by a professional tuner, as I do not have the entire know how to do it myself or the facilities.

Tom

[svxistentialist]

Originally Posted by TomsSVX

Joe I understand that fully. BUT I cannot run any more than 12psi without have a chrank pulley made the half the size of the engine. Not to mention that would be well over the efficency of the blower. I do plan on doing this in stages. Firts things first, i need to get my rod bearing replaced which has been stamped. Once that is taken care of I intend on following through with an end user programmable EM, most likely the hydra that Boxer6 is working for simplicity. Once those two things are up and running, the water/meth injection would be next to see how well this is actually working. I will have two EGT sensors and an intake temp sensor at that point as well to see what the cooling is actually doing. Once all is well with the supercharger and EMS, then I will be working on some form of a twin charger. The EMS will be tuned by a professional tuner, as I do not have the entire know how to do it myself or the facilities.

Tom

Excellent Tom. You are working incrementally, then moving on, that's the way to do it.
Here is a chart that may interest you relating to the output of your 1600AX. [I was expecting you to be dropping to a smaller drive pulley on the blower rather than a bigger one on the crank, but I see what you are at OK]

EG33 hp.....@psi... sc drive ratio... sc rpm
280 ......... 4.8 .... 1.21 ............... 6647
300.......... 6.3......1.30 ............... 7168
350 ........ 10.2 ... 1.54 ............... 8486
400 ........ 14.1.... 1.79 ............... 9827
440 ........ 17.3.... 1.98 ............... 10915
450 ........ 18.1.... 2.03................ 11189

Now as you already know I'm sure your twin screw is rated for continuous rpm of 13,500, and none of these outputs are anywhere near that.

This gearing presumes that the EG 33 develops max hp around 5,500 for these numbers to make sense.

When you get your Hydra and your sensors and your water/alky mist injection, set your pulleys for a ratio between 1.8 times and 2 times, and you will definitely get over 400 horse. With no strain on the blower!!

Joe