They are just fluxcore injectors, the new Edge hot box and BullyDog boxes stacked, and our hybrid turbo unit. Stock manifold, stock IC...etc..etc. We are working on a new single turbo to make even more power and its an MP unit so it will be priced very nicely.

Jose

 

I'm getting some value from the responses...

The old "tell me how fast you want to go" response is sometimes like shutting down, that is the obvious answer to something like this...

So how about this....

900rhwp, assume 3200 raceweight...

540 BBC
454 BBC
402 LS1
346 LS1

Any turbo.

The 540 + any turbo wins again right? The generalization I'm after is that, given no limitation on turbo size, the bigger cubes wins.

 

And... sure the piston velocity might mean that the bigger motor will have beat up cylinder bores faster, but I was not using that as a limiting factor.

You could tune/boost control a big inch setup to the point where you don't have 1220tq at 2500 rpms and the combo would be faster than the smaller inch setup.

Or... am I wrong?

Is a 540 BBC + __ turbo (assume the block is the same weight as a 402 LS1) going to run the same as a 402 LS1 + __ turbo?

 

No, ALL pistons engines have slower piston movement at the bottom than at the top because of the kind of motion that a piston engine sees with a connecting rod. The longer the rod is the more it approaches what you are thinking about.

An infinitely long rod will basically cause the pistons to have sinusoidal motion equal at the top and the bottom and the shorter the rod gets the more time it dwells down at the botom and swings through TDC faster.

 

I would say yes you are right that the bigger engine will win if all of those guys have the same turbo but it will just operate at a much lower rpm. I am just getting into the turbo stuff deeper but there are almost no classes in regular racing where they will even allow you to do that but on the street of course you can do anything.

 

Why is this? What is a general rule for estimating the egt's and backpressure?

 

pro stock are you planning on building a turbo car? sounds like it

 

So based on what Jose and others have said, the big inch motor will come up on full power much sooner, and will make the biggest torque. My 540 BBC example might make big power, but will need a huge turbo so as not to 'run out of' turbo.

So with turbo efficiencies, what is the rule of thumb? What range should folks shoot for?

 

I talked to jose earlier today that dude is cool as **** called me on a saturday to talk about engine and turbo combinations lol...i just have to do some thinking of how much power i want to make on the street...its between a 366 or 408 setup think i might be going with the 408 setup cause i plan on getting a T88 down the road but if i dont then a 366 with a T76GTS will bring on some pain...he was a big help

 

Is this because different distances are covered related to TDC and BDC? For instance.... is there more distance covered between TDC & half stroke (where the crank is at a 90 degree angle with the bore) than between half stroke & BDC?

 

For street going turbo cars I am a fan of stock displacement engines.

For really hot street and strip cars turbo cars I like to destroke a bit.

Its not entirely a lower displacement thing but that increasing the boost to get to a power level is nowhere near as hard on connecting rods as stroke and you have a more efficient engine. Its how much of that displacement will get used to what %.. If money were no object i would have a ~302 built on a LS2 block and twin garret GT series bb turbos.. We are getting Hp in the 1k+ range on 2.0 4 bangers.. Even with a OHV based engine which is essentially 2 2.5 liter 4s sharing a crank you can hit ~2k hp... W2W and Ken D have done it..

You can hit (with in reason) your power level of choice with your choice of bore and stroke combinations. However each combination will have its own pros and cons.

On a car that is'nt tubbed, spooled or tube framed you can still have traction problems at or under the stock disp with a potent turbo system.. On these cars I put more priority into ripping down the track once out of the hole than massive power at the line.. You will still have alot with a drag anti-lag system just not at the expense of a wider power band..

 

Yes and I put a picture below to show you the only way to achieve the symmetrical motion some people think happens but with a regular length rod. The only way to achieve this is with a rod like in number 2. Of course we don't have rods like that but it's just an illustration I did. Number 1 is the normal rod and piston and causes the irregular motion in the normal reciprocating internal combuston engines we also all know and love!



With a regular rod and crank setup at 90 degrees you are always already below half the stroke distance down the bore from TDC.

With an LS1 and a 3.622 stroke and a 6.098 rod at 90 degrees you are actually 2.09 inches down the bore so you are past half way down the bore as far as the total stroke in inches and yet you are at only half the stroke in degrees. The last or second 90 degrees of stroke to the bottom only moves the piston 1.53 more inches and in fact in the last 45 degrees of last 1/4 of stroke the pistons only moves from 3.23 to the bottom of the bore at 3.62 inches or a total of only .39 inches.

So we see at the bottom, the piston moves from 45 degrees before BDC to 45 degrees after BDC the piston only moves up and down .39 inches and sweeps .78 total inches but at the top near TDC when the piston moves from 45 degrees before TDC to 45 degrees after TDC the piston moves up and down 2.09 inches and sweeps 4.18 inches!

Like I already said ALL piston engines are like this but the effect is slightly more exaggerated the shorter the rods are at any given stroke.

 

The piston Gs and friction HP graphs are of a 88mm vs a 100mm stroke.. I know WTF... Its a import comparison but the only cropped screen shot of EAPro graphs I had on the HD... 88mm stroke is close to a 350 chev (3.465) and the 100mm closer to a 4" stroke or so (3.937)... Also both are 87mm bores so the friction levels will be lower but the same % of difference will be present at 4.0.

Notice the more sinsuidal motion on the 88mm stroke with 162mm rods vs camel hump BDC g forces of the 100mm with 150mm rods. The 88mm has still got some BDC dwell but does'nt yank the rods around.. Yes the long stroke yanks the piston to over 7000g's. Thats at 10k rpm but the graphs stay the same shape at 5k with a different scale on the chart...

Also look at the friction HP.. Both engines in this case are set up with low tension rings and a vacuum pump. I had data.. erased... of std no vpump setups and the friction loss gap widens as does losses due to ring flutter. The 100mm will flutter alot more and alot easier..

IMHO the bore stroke ratio on a stock LS1 or LS2 is really nice the way it is for the kind of powerband most people want.. With higher boost engines I prefer a bit more oversquare than stock..

 

Wow, I never ever thought about all that.... good information though! I learned something today! Thanks for the input!

 

This is all true at the SAME rpm but these two engines will make power at different rpms. The change in loading from rpm is much greater than the change from rod stroke ratios. Stroker engines can make the same or more power at lower rpms than the smaller and "better" rod ratio stuff will which makes them stay together for a lot longer ultimately. All else the same the better rod stroke ratio should result in a little less wear and loading but if you are getting the worse rod angle from a bigger stroke the rpm is also going to be lower in general too so the bigger stuff tends to be less stressed in almost every single way and yet makes more power as well. There a reason Lingenfelter's turbo was a 427 LS1 and not a 346.

On your simulation make the two engines you were showing have the same piston speed which they will be close to if they had the same heads and cam and see what the loadings looks like then!

 

You can also see that at the same piston speed the stroker will have LESS friction according to your chart.

At 9000 rpm the smaller 88mm stroke engine has 40 hp of friction loss according to that chart whereas at 7920 rpm the 100mm stroke engine seems closer to 38 hp of friction loss. They are both running the same piston speed at those rpms.

Basically in real engine tests it is usually worse that that on the small stuff. If both engines could achieve the same piston speed due to heads and intakes and manifolds etc. the resulting 13% higher engine speeds of the 88mm stroke engine will result in 29% higher loading on the rotating assembly than on the lower rpm 100mm stroke engine. Another words rpm piles load on at the SQUARE of the rpm difference where as stroke only is a linear change IF you are looking at the limiting pistons speed of the engine in aero and breathing terms. You can always get more piston speed safer with stroke than with rpm.

 

so many numbers! ...have to learn it all!

 

This Thread kicks ***

 

I would have to agree Eric, the bottom line is at least in my experience, the larger engine will allways prevail if set up correctly, obviously if the turbo used was FAR too small it would be a problem but the same holds true for too large a unit as well. Realistically, horsepower is only a measure of torque multiplied by time which means what moves the vehicle is TORQUE. So reguardless of what RPM you are at if your vehicle makes considerably more torque even at 4000 rpm, if you gear it properly it will likely perform better than the smaller higher strung engine making less even if the HP is slightly better. Also something to remember in all this is the fact that the larger engine will do its job MUCH easier than the higher strung and therefore less reliable small engine, they all can be made fast but from a reliability standpoint the bigger engine will win in the long run every time.

-Bryan

 

Thanks Bryan,

Yes the turbo can be in it's sweet spot with many different engines and the larger engines are probably easier on parts since generally they slow the rpm down. It is true like Jose said that you want the right turbo for the right app as far as horspower goes but you can use a 76 to make the same power with a 346 OR a 408. The 408 will just be a little nicer and boost quicker all else equal. There are different exhaust sides I guess if you wanted to raise the rpm even on the 408 with the smaller turbo since you will have somewhat more exhaust and you could lose some of you backpressure maybe at the expense of spooling.

I would say that as long as you design the engine to receive the boost at the right range you should be able to keep everything very efficient. If you try to run an overly large or overly small turbo with your engine at a particular rpm you will probably not get the results you could have with the right parts. I just do not believe you will be "better off" with a smaller engine with a smaller turbo. I would set yourself up to make more power in the future with a larger turbo and just go with the larger engine right away and set up your smaller turbo system to work with it initially.