Ok, this is my first time posting a new thread in advance tech, but hey, if I don't go to the experts, how do I know I will be getting the correct/best information.

Here is the objective: 1000 hp out of LT1

Path of approach: Twin turbos, likely Garrett 60-1's but not sure yet and not asking this.

I have done some figuring on paper concerning what I need to get there in boosting a motor with different cubic inches of 350/383/396, and I have come up with a figure which should support a T60 setup quite well, just at different levels of boost and should achieve it on street gas with some type of supplemental injection system.

On to the question. What type of volumetric efficiency can I expect to get with such a motor? What type of flow numbers would my heads need to achieve something like 93% VE at 6000 rpm and above? This will not be a race car. Just a very over modded street car, if there can be such a thing, that will see some drag strip and some open track time, so useable power is much more important than peak power.

Car is in the sig.

Thanks,
Jon

 

Jon,
The whole point in supercharging is to achieve better than 100% volumetric efficiency. You should see ve on the level of much better than 130%. Even better than 100% can be made normally aspirated.
1300 hp is a tall stretch for a small block on pump gas. You are going to need a serious cylinder head and a well built combination. This is an area I haven't seen too many people go with a smaller small block so I can't really say anything about what's needed. What I can say is that as much cylinder head as you can get..... get it. If I were attempting to do this I'd pull the sb2.2 out and use them. Not a cheap build with such a specialized head but power at that level never is.

-Mindgame

 

I am talking NA volumetric efficiency here. The motor's ability to flow air without boost plays a large part in the selection of turbos and boost requirements. I know that as boost goes up, so does the volume of air in the cylinders. I have figured that a 350 will need a VE of over 200% at around 24 psi boost in top tune. Would I drive it like this normally on the street? No, but that is where variable stage waste gates come in. I don't have my calculations here with me, but I think I am on the right track here, or have I missed the boat?

Should I have posted this in the Forced induction section instead? I figured this was the right place because I am looking for NA VE numbers here.

Thanks,
Jon

 

Will my heads need to flow in excess of 270 at .600 intake and 200 at .600 exhaust with very high numbers throughout the scale?

I don't have any engine dynoing software, otherwise I could design this myself. I need your help, folks.

Jon

 

Jon,

Better than 100% ve is plenty attainable on an n/a motor. I've built a few engines that were in the 115% range and I aint a pro. It's just a practice in using components that work well with each other.
As for the ve off the boost, I can't say. Most of the cylinder head work for sc'ed engines is a bit different than for those for n/a in that a forced engine may like a much larger head than it would being n/a. Pushing the charge is going to raise the velocity through the port so the size plays a bit less importance there. The thing of it is..... it can be hard to find info on supercharged head work and what the goal is there. It's kinda like a black art thing that some really good engine builders know and don't talk too much about.
I remember reading here a while back that Mike Moran's 4-turbo motor was using a bbc head with smaller than typical port volume but of course they wouldn't say much else on the subject. So I scratch my head.

Maybe someone here has dealt with this in their shop or has worked in this area on race engines.

-Mindgame

 

dont even look at the .6" flow numbers unless if your runniing above 6" of lift. I would reccomed 220cc then have them ported they should flow what you need. Ive used the turbo calc http://www.turbofast.com.au/javacalc.html for compressor flow and hp but there are alot of varibles. If your running a cam with 109 lobe sep and a high duration exhaust it will make more power n/a wich is what your going off of. But once you put the turbos on you will have an extreme case of reversion (reverse exhaust flow) esspecialy at high boost from the backpressure. A turbo engine and a n/a engine are 2 totaly diffrent animals. I would reccomed for you to further research as much as you can about turbo engines and join the diy-turbo at yahoo and import forums (yes some of them actualy know alot about engines). The diy forum has some good turbo knolegable people and good techincal theorys and ideas are discused.

If you want desktop dyno you can download it from many download sites if you look around. If not than i can send you my cd of desktop dyno 2000 so you can install it then you can send it back. But whatever you do dont make copys of it if you have a cd burner .

A pointer about desktop dyno with the new turbo option, dont even touch the turbo option. I say this because its not accurate at all. You can plug in a terrrible cam for a turbo but good for n/a with alot of overlap and the power will go up . I dont think the desktop dyno programers put alot of work into the new option, They dont even have the turbine trim options and that is critical for a turbos operation because it is one of the main components that determines the backpressure at evry rpm, turbo lag, and pressure ratio. The blower option works well though because of the less complicatin sue to all they had to do was figure out how much extra air was being forced in and how hot the air will be then just subtract the hp to it takes to drive it. The best adn only real way to test a turbo engine is a real dyno, or g-teck pro using massive slicks so you dont spin the tires (heard g-teck is accurate as long as you calibrate it to your cars actual weight) If anybody know of any accurate and advanced turbo engine programs please notify me.

 

Thanks a lot guys. I will be doing a lot more research concerning these things over the next couple of months.

I second that request for some good software which analyzes a turbo engine. I had better look for desk top dyno in the mean time.

Jon

 

A few oversimplified thoughts...

When discussing VE on a turbo engine there is a significant difference if you’re talking about at the turbo inlet or in the engine, and making sure that you consider both is pretty important in figuring out what you’re looking for. The VE of the actual engine does not change, and ports flow largely the same as they would NA. The difference is that the compressor has now increased the density of the air in that port so the same volume flow is a greater mass flow of air.

When trying to figure out the actual mass flow of air for a complete turbo engine what you really need to have is some approximation of the VE (or mass flow) of the engine NA, the VE or mass flow that you’re trying to achieve to make the HP that you want, and then based on that you can calculate a density ratio needed from which you can approximate a pressure ratio (boost) and finally you can look up that pressure ratio on a compressor map and see if that compressor can pump as much air as the engine will require at that pressure ratio to make that power.

If you could get whatever octane fuel you’d need to run with whatever boost you need to force the correct mass of air into the engine, then that would be the end of it. The thing is that octane is limited and that turns this whole thing into an iterative process to find a combination which will flow the necessary mass of air at a reasonable boost.

Cam selection and head port design is mostly based on the rpm capability necessary to force the necessary mass of air into the engine at a reasonable boost.

Usually it’s fairly difficult to successfully run more boost then works out to be a density ratio of 2:1. Density ratio rises significantly slower then pressure ratio because as boost goes up compressors tend to add heat to the air being pumped (this is what is meant by a compressor’s adiabatic efficiency), and how close your density ratio comes to pressure ratio is dependant on that adiabatic efficiency (now hot it gets) and intercooler efficiency (how much you cool it down). Without an intercooler your typical turbo will reach a density ratio of 2 at pressure ratio of just over 3 (about 30 psig boost at sea level). If an intercooler is used then the density ratio gets closer to the pressure ratio as the intercooler removes more heat from the intake charge (the way most compressor maps are drawn if the intercooler can achieve an outlet temp of 80* then they will be equal)

To give you a GREATLY simplified example, lets say that you want to restrict yourself to a density ratio of 2:1 You’d need about 92Lb/min air to feed 1000hp. Assuming that you have a compressor supplying that mass of air at a density ratio of 2, the engine has to be built to have a mass flow of roughly half that at the rpm that you want to make that power, 46Lb/min, which works out to be about 670cfm. Now assuming 100%VE (could be anything from 75 to 125, depending on the engine design), this would mean that you’d have to turn a 350 to about 6600rpm, 383 to about 6000 and a 406 to 5700.

Of course, if your engine combo has a better or worse VE, that rpm will have to be adjusted, if you cannot run that pressure ratio (again, between 15 and 30psig at sea level depending on the intercooler) you’ll have to turn more rpm or find more VE…

WRT to camshaft selection, it has to be tempered by your exhaust turbine selection, the smaller, more restrictive, faster spooling your turbine (and exhaust system in general) the smaller the cam has to be and the more lobe separation you’ll need to prevent reversion due to pressure in the exhaust port.

BTW, don’t waste your time on DD2000. The turbo modeling is awful. As far as I can tell there is no limitation to what any of the turbos can flow and related to that, they don’t seem to model exhaust restriction at all. The end result is that you will always get the most power by using the smallest turbo just because it will spool/build boost the fastest.

 

WS6 TA,

Thank you for the help. That was exactly what I had been previously led to believe. Which is what brings me back to my original question.

If one were to simply forget the effects of the cam and the turbo for a moment, what type of flow numbers would my heads need to have to achieve an NA flow rate of 612 cfm for a 350 engine assuming a VE of 93% at 6500 rpm? How about if the engine were a 396 pumping 692 cfm assuming the same VE and rpm? What would have to change in order to bost the VE of the engine in regards to the heads. I am just trying to pick the heads and intake here folks, so any help you can give me in this area is greatly appreciated. I know that these are all interrelated variables, but, if I can limit the effects of one variable at a time, I know that the end result can be more easily achieved.

Thanks,
Jon

 

Where are you geting these figgures from? if your building a turbo engine buy 220+ cnc ported heads, single plane intake or some type of good efi manifold, and have a custom turbo sold roller cam ground for you using the specs reccomended by the cam company. To change the VE you not only need more head flow but more cam and manifold size. go with the 383 simply becaue you will make more power everywhere and spool the turbos sooner becaue you wont need as much boost compared to a 350. 60-1 is too big for what you want you need a pair of to4e .50 trim. I pluged it inot turbo map (below) and it gave me
after screwing around with desktop dyno i could come up with this i dindnt play with igntion and cam advance retard so there is a little more power to be had.

rpm ve
4000 86
5000 88
6000 82
6500 76
7000 72

Plug it into the turbo calc and play around thats the best way ive found so far. But it still dosent take into acount the turbine size.
compressorshttp://www.turbofast.com.au/turbomap.html

After i pluged it in with 70* air and %75 intercooler eff, 25 lbs of boost. 997 hp at 6500, 1017 hp at 7000

You cant have a high ve due to the low compresion ratio, it weakens the pulses but is needed for a turbo engine to live with boost. On desktop dyno the cr is at 8.5 the heads are brodix track 1 heads. The cam is 115 lobe sep 110 intake centerline 250 int 240 exh dur. Do you want my desktop dyno cd if you do email me your address.

 

67LT1Bird, I think that you might be slightly missing the point on the VE and airflow (or I’m misunderstanding your question).

Airflow to produce a set amount of power always stays roughly the same assuming that you maintain the same overall engine efficiency (we harness so little of the actual energy in gas that that really doesn’t change that much). The approximate 670cfm at a density ratio of 2:1 will be the same whether we’re talking about a 151ci 4 cylinder or a 600ci mountain motor. That is the air flow that you’ have to mix with the fuel to make that power.

Volumetric efficiency just defines how well the engine is able to pump air in and out. It’s a measurement of the overall system. If you have a set amount of boost that you can run and your VE is lower that only means that you’ll have to turn more RPM at that same VE to pump the air. VE is not really dependant on the size of any particular part, but of how the parts work together. In a perfect world, you’ll achieve a better VE with smaller ports, intake and exhaust, which will not only help the response below the power and torque peaks, but will make the VE #’s more easily achievable because the velocity can result in additional intake charge inertia, ram tuning, swirl in the combustion chamber, better scavenging… all of which will help fill the cylinder, increase combustion efficiency and/or lower detonation sensitivity. Any of these will increase VE (this is all assuming that the cross section that the gasses flow through never gets too small to flow the required air without posing a restriction).

Higher VE is all dependant on getting all the parts working together better. If you want that high VE at a relatively high rpm you need large ports, large intakes/exhaust big cams… But because you’re talking about a blown application you really don’t have to turn the engine that high, you can move the air using the blower.

There are some rules of thumb that assorted people/companies use to guess at the correct port flow for a specific goal, but they are just that, they’re a rule of thumb that will get you in the right area but if you manage to make it work is dependant on the combination and tuning. I think the most common one is the AFR one which is something like:
HP= CFM flow of an intake port * number of cylinders *.2575
If we’re still working on the assumption that we’re staying with that same density ratio that equation would predict that you’ll need a head with an intake port that flows 243cfm.

Given no rules or available parts restrictions, you’re really best off running as large and engine as possible. Everything else being equal, a larger engine will be able to flow the required amount of air (and make the power) at a lower RPM, making for a more durable, reliable setup. The one place where this might screw you is that you will be making more torque (torque is always proportionate to displacement * VE), and since we’re talking about basically insane power, higher torque production will make the car less drivable (unless you know of some secret that makes it easy to hook a few thousand foot pounds after gearing…, and I’m sure the rest of us would like to hear it if you do).

WRT choosing an actual turbo a lot of it depends on how good an intercooler you’re going to run. Like I said already, not running an intercooler or running one that isn’t that efficient will require significantly more boost then running a good intercooler. To pump the same mass of air at a higher boost you need a smaller turbo. If you can’t picture that look at a compressor map and notice how with the same mass of air you move closer to the surge line (too big a turbo) as the pressure ratio goes up. Based on that and looking at the few compressor maps that I’ve got sitting around, a 60-1 looks like a reasonable choice for an engine that runs a decent intercooler, which is a fairly safe choice because unless you’re going to run alcohol or extremely low compression on race gas, you’re not going to get the engine combination to work well without an intercooler (honestly, I’ve got a map for a T61 that looks PERFECT for the entire range that you could possibly see with or without an intercooler).

turb0racing- I’m pretty familiar with the maps and calculators on Ray hall’s site, and I would agree that they’re a pretty good way of getting a good feel for what will work and not work, but there are a couple of deficiencies. The 2 biggest are that the turbo calculator chooses turbine sizes that are large enough to almost not need a wastegate for the application (most tend to have success with at least one step smaller), and it tends to choose compressor sizes as small as possible for the application (I’m assuming for better spooling targeted at street use), which does not put you in the most efficient range for the turbo and would not be a good choice where you’re trying to optimize for power production. Looking at the T04E maps, they’re all on the ragged edge of too small for what would work for 1000hp, and would produce more heat in that application then a larger turbo would.

If you guys are looking for some good, quick reading that is not too technical but gives just enough details to understand most of this (and gives the math to show how he gets there if you care to learn that) grab a copy of “Turbochargers” by MacInnes

 

Thanks guys,

I do already have "Maximum Boost" by Corky Bell, which I really should step up my reading of. The 1000hp is just a nice round number, but I will be satisfied with anything in the 900hp up range while running on maximum safe boost. I probably will also be running an alcholol or water injection in order to bring up the safe boost range while running pump gas.

Jon

 

Using the numbers form desktop dyno (my previos post) pluged into the turbo map not turbo match the 60-1 pu the air flow in hte upper left side of the map right next to the surge line in the first outer island. The to4e .50 placed all the rpm at the top (because of high boost) of the secondary effeciency island of 76% simply because of the beter efficency you will gain hp. The 60-1 is just too big check i out.

I read the turbochargers book too its worth the money, but i feel there wasnt enough material about designing turbo engines and how they affect the engine. But you cant get everything : )


http://www.turbofast.com.au/turbomap.html

rpm ve
4000 86
5000 88
6000 82
6500 76
7000 72


And i forgot to say the ve. I gave you is on a 383.

 

Grrrr… I can’t find my copy of DD2000 to try to model something that has more reasonable #’s for what I would consider a high performance engine…. I can find directories full of head and cam files on my file server, but not DD…

Anyway, turb0racing, I understand what you’re saying, but I don’t agree with now you entered the #’s and your conclusion…

To start with, with anything that large you will not have full boost at lower rpm’s, to approximate that I entered the points you listed as 10, 15, 20, 25, and 25psi boost, and used all of your #’s and found that the last 2 points went up or past the max rpm for the 50 trim. I also noticed that the turbo efficiency and air temp didn’t have any effect on the output (should be similar to increasing or decreasing IC efficiency).

Second, most really serious, well built engines will have VE’s closer or over 100% or higher at their HP peak, a car this serious is fairly likely to be running a big IC or even ice water cooled… Just about anything you do to the basic combination will require a larger compressor.

Really the argument is somewhat academic, both will work. If it was me I would just prefer some room to grow with the combination, and for that matter, I’d try to shoot for a combination that would make the power at a lower RPM… both of which will require the larger turbos.

 

That motor was a race motor but like i said it had a 8.5 cr and that weakens the ve with a 11:1 cr it gave me around 500 hp and a 95 ve. You dont only gain power from the higher squish when compresing the air you gain power because the vacume is stronger sucking and blowing the gasses into and out the engine. Also the turbo cam isn best for n/a power that would complete the combo to run a 100 ve like you are speanking of. I and doubt that even Kenny Duttweiler never built a +100 ve (without turbos on) turbo race engine.

I still dont see how you think the 60-1 is better. The .50 will get a 76 effeciecy all thorughout the rpm and the 60-1 is in the 60s. About the over reving both turbos are at nearly the same revs the 60-1 is is at 114 k rpm and the .50 is at 116 k rpm . Look at compresor flow maps on the ray hall site to see the .50 rpm numbers and see whet turbo map plots it. The diffrence from 65 (60-1) to 76 (.50) effeciency you lose 20 hp. You have to manualy change the effeciency for each point on turbo map using the flow map points. Thats why you werent geting any diffrnence in hp with the diffrent compresors. I know the boost isnt there at low rpm and pluged in in a simmilar way you did i puged in 12(wastegate opens),23 24, 25, 25.

More power at low rpm would mean you need smaller turbine size- bigger turbos high rpm, smaller low rpm. There is realy no room to grow unless if you plan on more ci like a 427 or a 406. I would consider growing just using a water to air intercooler and more boost and a less overlap cam to take advantage of the extreme boost. If you are running a race would you buy a pair of shoes that are too big or just right?