I logged boost on the AEM vs TQ on the dyno. Peak TQ occured abour 250rpm past full boost on a 10.5 turbine stock turbo.

 

i think he was just stating that if we ran 30psi it woudl make over 600awhp.. which yes that is true.. I PMed you the mods of the car already that is being used in this discussion!

Mark
SBR

 

Correct, and taking into consideration turbine wheel size can change torque reactions on a graph. As to comparing it to a supercharger that doesnt have a turbine wheel but a pulley running at rates correalated to the engines rpms as i stated earlier..So a larger turbo will not act the same as the stock turbo. Yes a turbo and a supercharger supply an engine with air in a similar fashion, but how they make the air flow is drastically different. You think an engineer would see that..

Mark
SBR

 

What kind of ex. mani are you guys using? Like design/company wise or is it an in house? Im wondering because i cant seem to find one listed on your site. Also this is stock intake mani correct? These are once again sick *** numbers. BTW you wouldn't happen to know a kid named todd would you? He talks about SBR all the time he drives a 2g with 502 whp, license plate donkeypunch (dnkypnch)

 

Yes we know todd from SC.. He is good customer. Runs our 6 bolt engine is his white 2g. on the EVO we ran a DNP header with the T3 flange and our custom O2 housing. But, we will have our own cast manifold and O2 housing out soon. No it was a Magnus Intake manifold. and thanks for the props..

Mark
SBR

 

Your degree does not mean much when you do not know what your talking about. How many small displacememt turbocharged motors have you built and dynoed? Can you even read a compressor map, or understand the equations I asked you to look up? You DO NOT HAVE max torque when you have max boost on a small displacement motor with a 65 lb/min turbo. Its just that simple. Do a little more research, yes VERY GOOD resources can be found on the net if you know where to look.


5% good information, the rest is garbage.

You are not even close to understanding, so please quit referencing a supercharged Mustang.

Superchargers work the same way as turbochargers eh? Good one!

Torque will increase with RPM, as will HP since HP is a function of torque.

A little research here will explain why at 3k a 65 lb/ min turbo making 450 ft/lbs will twist a connecting rod faster than you are willing to understand why.

Do you assume my 707 WHP DSM should make max torque at 4200 RPM's where it reaches 30psi? If yes, explain.


I understand Hp is a function of torque, I also understand EVF = (engine CID/1728) * (RPM/2) and N = (P*EVF*29/10.73*T)

Read up a little on VE, and read up a little on reading compressor maps. Then, and only then will we have an intelligent conversation.

Run the numbers, you will understand.

Again, compressor maps, VE, among other things.

Please try not to take me the wrong way, I just want to make sure everyone has good information, but without me doing all the leg work. We can have a little fun with this if we go about it the right way.

Agree?

MGH

 

i know that head design and stroke have a lot to do with torque. the neat thing about the stroker crank is not only does it increase displacement slightly, but having longer throws on the crank itself inherantly increase torque (longer moment arm, thus more torque). i thought i mentioned the intake manifold properties, as well as headwork, and valve lift. but on our cars because all of this stuff is constant, long stroke characteristics don't make a difference at high RPM's or low RPM's. it works the same way at both levels (which is a good thing). the head work and air flow design properties also make a difference but no so much that it would push your torque curve over by 2000rpm. ideally, your only going to gain a tiny bit of power from designing manifolds for high RPM's so on a torque curve you will see the torque increase as the boost increases, until the boost reaches what it was set at, then the torque curve will fluctuate minimally, and increase slightly as the engine speeds increase provided your holding boost steady. the best torque curve will remain flat all through the rpm band, showing that flow properties are ideal for all RPM ranges.

keith, what boost levels are you using, what sized turbo, and where did your boost level reach set pressure at? i bet it is a lot closer then 2000 rpm (and i would bet within 500rpm), and if you use my following formula, i bet it is within 100rpm.

i think we need to coin a new term for engine dyno graphs. we will call it the torque rise time. this will be where the torque has increased to within 10% of peak. for the cobra plot i posted, his rise time was the instant they started the dyno, or about 2000 rpm. even though the torque increases slightly, he is within 10% throughout the entire run. for this 550hp monster, i'll give him 455ftlb of torque max*.9 = 410 ftlb, at 4800 rpm. i will call this his rise time, which is where he is just maxing max boost. he is not making max boost at 3500 rpm because he is only making 160 ftlb of torque there, and if head work along makes a 200% increase in power over 1500 rpm, then you should get a job with ferrari F1.

 

haha... ah this is getting amusing now.

i'll respond to this one shortly...

but you don't need to do hardly any leg work at all. all i need to see is a plot of the engine making max boost at 3000-3500 rpm. once i see that, i will concede defeat.

 

Heck, that's true for everything you read on the 'net! Can we recap for those of us in the peanut gallery trying to follow along?

If things were really simple, would you expect maximum torque when you have the highest manifold pressure (boost)? Sounds good, but things aren't that simple. What if your turbocharger were really inefficient at this point and the reason the manifold pressure is high is because the air is hot? So maybe something like the highest ratio of pressure to temperature is the key. Dust off PV=nRT and rearrange and that means we're looking at the point of highest air density in the manifold.

That sounds better, but what if the engine's volumetric efficiency is low at the RPM you hit the highest density? Then you can't take advantage of all that air. Is that getting close to the point here? Seems like there are enough variables that it would be hard to pin down just where the torque peak will be.

Dave

 

anyways.....i'm getting lost with all these terms..lol


just get that water to air intercooler on the way...the one that u could use with ur normal intercooler!!

 

wow this is a good topic!!! sbr there are a few dsmer's here in slc ut that use your products with nothing but good things to say.. impressive #'s good luck on the 15th

 

alright i will try to answer these all.

to start i keep referencing a mustang because it shows a nice level torque curve. something that is typical of supercharged engines.

superchargers don't work the same way as turbos, but they absolutely perform the same task. they both compress the air going into the engine. if you somehow misinterpreted that, i'm sorry.

now to show that you need to review your physics, explain to me how torque increases with RPM. i will draw you a diagram of how to calculate torque if you like, and in the equation for torque, there is no RPM, and no time. it is a time independant variable, and therefor is not related to RPM. there is however one property that does effect torque that changes with RPM, and this would only be cylinder pressure. if you had a NA engine, torque will remain level throughout the rpm band, as cylinder pressures remain relatively constant. if you want me to show you a plot of a NA torque curve just ask. for a turbo engine, once you reach full boost, your torque curve again will remain relatively constant because the cylinder pressures will be close to the same (assuming your intake temps remain constant too).

why will a 65lb/min turbo twist a connecting rod at 3k rpm pushing 450 ftlb of torque? you don't seem to realize that torque is a FORCE and 450ftlb of torque at 7000 rpm is putting the same stresses on the connecting rod as it would at 1k rpm. there are other stresses involved such as G loading on the piston at high rpms, as well as drivetrain reactionary forces at lower rpms, so the stresses are not going to be identical, but you get the point hopefully. hell, my grandpas truck generates 500 ftlb of torque at 1k rpm, and he doesn't twist any connecting rods...

post up a dyno sheet of your 707 hp dsm with torque curve, hp curve, boost curve, and tell me if your running any additional fuels (such as spray, or anything to spool the turbo up faster). i will explain anything you want (or possibly be proven wrong...).

congratulations on posting up the two equations. now interpret them for me the second is just PV = nRT rearranged. simple equation... the first can be read with a MAF sensor (or mass sensor to some). it just just the volume of air flowing into the engine. also a simple equation.

volumetric efficiency will remain relatively constant when comparing a 4g63 to a 4g63 with a bigger turbo. this property has more to do with cam lobe properties and air flow properties, and regardless, will be very similiar of two of the same type of engine.

i can read compressor maps, so explain to me how your making 30 psi at 3500 rpm with a GT35R (and amzingly only making 160ftlb of torque)... i'll tell you what, i'll take the liberty of showing your wrong.

first, sense at 3500 rpm your map shows only 120hp. 120 hp calculates to approximately 15lb/hr of mass flow. if you claim to have 26psi at 3500 rpm, then that is a little less then a pressure ratio of 2. on a GT35R map amazingly your way into the surge area of the turbo... thats not good! it means your turbo is WAY to big for the engine and your damaging it. or the more likely answer is that your not at full boost until say, maybe 5000 rpm.

i totally agree with your last statement. i feel many people on here have a ton they can learn from an intellegent conversation on reading dyno charts, and compressor maps (among the many other things we are discussing). although i am no means an authority on engines, i do know enough to hold an intellegent conversation. i think i have provided enough to get an intellegent response back. i admit i have a lot to learn, and am certainly willing to. i already have done a little research because you had me questioning my own logic, but after further review i stick by my responses thus far.

 

bumpity bump.

 

Sorry, one of my employees was still logged in on my computer.....


Let's keep it simple.
You will get peak torque at peak boost & peak VE. If your boost holds steady, then typically you'll see peak torque as the engine comes on full boost. VE drops as engine RPM rises. Where your point of peak VE depends on many things but unless you have completely redesigned the 4g63 engine, it won't change drastically. If you changed stroke, bore, rod ratio, radically different camshafts, redesigned head ports, intake manifold, huge turbo amongst other things, you will shift your torque peak higher.
Every turbocharged car that I have dyno'd makes peak torque at peak boost, then plataeu's and drops.

Torque is directly related to cylinder pressure. Cylinder pressure is directly related to VE and boost. Are you sure you are not getting boost creep?

-Martin

 

Now if I have you right, you are talking about a stock car.. where on a stock turbo this would be close.. but now going by what you stated even to keep this conversation going. These changes will shift the TQ peak higher.. so lets look at what all was done:

If you changed
stroke,--- yes
bore,---yes
rod ratio, radically different camshafts,---yes
redesigned head ports,---yes (severly ported)
intake manifold,----yes
huge turbo----yes
amongst other things,---yes again

you will shift your torque peak higher. --- and isnt this what happened that everyone is discussing?? lol


And in a earlier post there is a Dyno graph of a stroker engine making similar power curves as ours. No when did you see full boost on that car?? my assumption would be between 3-3500 rpms if you tuned it right. Yet your peak TQ was not near that aswell..


Mark
SBR