mark kibort

Greg, I wasnt making definite positions in areas I didnt have some facts on . I was ONLY speaking of what I do know on the topic and that was in the area of the losses due to gearing and dyno methods and results on the track. You are confusing the facts with your hypothesis. I was taking the high level review of the topic, and you are in the weeds. Thats fine, Its all good stuff. But, go back and review your facts and formulas and see if there are areas where you could be misapplying them. For example, do you really think that the 4 valve heads will produce less hp than the 2 valve heads in the top end. as a note, we and others have done a test in reality,several times. a more agressive cam, one that is near the same, and guess what, the 5 liter bottomend mated to the 2 valve top end always seems to be shy on HP AND torque over the entire HP and torque range. It would be interesting to see a more optimized 2 valve intake like carls perform in an NA environment. anyway, again, I appreciate the discussion and your information with links. good information, but lots of other factors as well that havent been talked about that could determine an engines performance.
I think from reading your posts that you some how still think that dennis' engine cant make 375rwhp or 420flywheel. In actuality, its pretty unlikely that it doesnt based on what we do know about many of the losses. JUST the rolling friction alone on only the rear wheels is 20hp. add the front tires, and then an entirely additional factor. Losses through helical gears.

So, if you think about it, you chimed in with a Definitive "NO WAY is it POSSIBLE" attitude based on a BMEP factor. maybe you should tune it down a bit and just offer up a question on the occurance, rather than cutting it down.

yes, lighten up francis. Its all fun here!

mark kibort

I read the articles. good stuff.

Now, here is one of many dynos of a BMW with very little modifications. this is at the wheels HP and some do this curve with 2.8 liter, but this happens to be at 3.2liters. all stock stuff, just headers and ecu flash changes. (stock intake, heads, cams etc)

Using the formulas, this too would be impossible, or improbable, right? near 200psi? (BMEP)

slate blue

Mark, yesterday was a bad day, let's draw a line under it and move on. Just so that anybody reading this thread has unbiased information here is a post from another forum where I posed the question, how much power can I expect from my 2V stroker. Bear in mind that this engine has many of the best parts possible and excellent airflow and speed, non restrictive intake and exhaust all custom designed, cam lift will be around 16.5 mm or 0.650" Below is the answer, hopefully this also puts in perspective just how high this 200 psi number is.


"Greg,

Assuming Bishoff's engine was about 403 cubes (I'm too lazy to look it up), the BMEP @ 6500 power peak was about 205 psi. That's right in there with most of the winning EMC engines since 2002. BMEP is a good way to compare engines of different sizes/displacements/configurations, especially at hp peak rpm.

If you can do 205 psi BMEP @ 7500, your 367 would put out about 710 fwhp. My take is you aren't going to get there @ 7500. I think 190-195 psi @ 7500 would be very good. That's 660-675 fwhp or about what Tony got @ 6500 with .6L more.

If I was going to be discouraging (realistic?) I'd look at 170-180 psi BMEP @7500 or 590-625 fwhp. I think 500 lb-ft is possible for max torque.

My $.02

Jon"

O.K moving onto to sizing formulas to attain proper air speed, if we use the flow that the standard 4 valve heads achieve at GT cam lift of 10 mm which is around 270 cfm @28".

The formula is CSA = ( CFM / velocity FPS ) * 2.4

So (270/310) x 2.4 = 2.1 sq" O.K so just using this formula all you need is a 2.1 sq" port not the 2.42sq" port. That is just part of the question though. Can your engine use all that 270 cfm? Well if you can't you are losing velocity because the port is too big. The reason of course if your engine is not demanding 270 cfm then the air is not doing the 310 feet per second is it.

So then we have to estimate what airflow is required for desired power levels, Pipemax can help, it is designed to help sizing ports and pipes. So if you are aiming to achieve a volumetric efficiency of 110% which is very high btw, you can plug this in and you will find the average airspeed through the intake and exhaust.

Depending on how straight your pipes are that will effect on what speed you can run the air. (read the extra info from Larry Meaux below for limitations) Going back to the 928 ports, I ran another engine program with a 4 valve engine and made some presumptions. The program liked ports in the 2 to 2.1sq range with a 750 hp high revving engine, as I said before, the F1 ports are basically the same size as the 4V ports but they produce 100 hp per cylinder. So a standard 928 engine only makes 40 hp per cylinder, our airspeed is slow.

When my guys did some reco work on some 928 heads, I asked what they thought of the ports, first word was huge! They were surprised though at the power the strokers were making in all fairness. I am still waiting on pics of the filled 928 port.

Back to getting 110% efficiency from our 5 litre engine, I plugged in a redline/max power at 6,800 and that is around 455 hp. To get that, max draw or demand on the cylinder head is in the 230 cfm (usually it is best to add 20 cfm tolerance, so maybe up to 250 cfm) range and the recommended port CSA is only 1.63sq". That is the size required to get 310 feet per second at 6,800 rpm with 455 hp. Now for an engine with a Rod to Stroke ratio of 1.9, max demand occurs at 76.5 degrees after TDC. The program says that at 76.5 degrees the engine's demand for air is at 248.5 cfm, so at 250 cfm we are pretty much on the money.

If 250 cfm is all that is required then the first formula should allow a port size of 1.94 sq" but the program says 1.63 sq", I would probably go towards the larger size if you were just doing this once. The reason for the descrency is the amount of air used by the engine, not just the flow at max lift. My guys think I will have to build my engine 3 to 4 times to get it right, this is why I am taking my time to try and do it just once.


So you can see that this proposed port size is quite small to what we have, if we are able to achieve 455 hp with airspeed of 210 FPS then the port of 2.42sq" is O.K but that is what the air will be running at 210 FPS. That is very slow, let alone what a standard 320 hp engine would be doing.


Please read the next quote by Larry Meaux who makes Pipemax, it explains some important facts that are needed to understand why certain figures are used, like 28". Most flow benches are run at this depression, as such this is the standard. When the operators use the velocity probe it will be at 28". There is some other formulas too.

"the Mach # at 350 FPS = approx 350 divided by 1116 thats .3136 Mach ..the 1116 FPS Speed Of Sound depends on local mixture temperature and density

Speed_of_Sound_FPS = (( 459.67 + TempF) * 2402.625624 ) ^ .5 = 1116.32 fps @ 59 F

the FlowBench is steady-state constant depression/velocity and 350 fps = 28" Test Press. approx. but the correlation to Live Engine is that
350 fps at 28" on FlowBench maybe the same as between 614-700 fps
.627 Mach = 700/1116
.55 Mach = 613.8 fps

most People think that just because you FlowTest at 28" inches that everywhere inside that Port air will be flowing at 350 fps...
thats not going to happen unless you have a perfect, constant area, perfectly straight piece of Pipe.

you Calculate what the "baseline Mach Index " was, use the following Formula=>

FPS = ( Bore * Bore * Stroke * RPM * .003537 ) / CSA

CSA = ( Bore * Bore * Stroke * RPM * .003537 ) / 614

Larry M "


So the 28" formulas.

FPS = ( CFM / CSA ) * 2.4

CFM = velocity FPS * CSA / 2.4

CSA = ( CFM / velocity FPS ) * 2.4

I haven't got time to go any further right now as this is very time consuming, I will add something that is interesting for the 2 valve guys. I added adjustable cam timing to my engine, it has a very nice exhaust and tidied heads and intake. Every time I retarded the cams I lost power, when I advanced them I made more.

Why, why why, well I put it down to the very late closing of the intake valve, the air is very slow as such the air is just being pushed back out by the rising piston. If the air was traveling fast enough it would have enough inertia to keep ramming into the cylinder but it doesn't it, it is also traveling in the low 200 FPS range. So by advancing the cam the inlet valve closes before the piston can push the charge back out. That is my theory anyway.

Greg

slate blue

By Mark Kibort
The sum I do is as follows, 286 rwhp divided by 0.85 =336 flywheep hp x 5252/6500 rpm = 272 x 150.8 = 40,997.72 divided by cubic inches of 198 = 207 psi. Mark just refer to the above post when Jon responded to me, I think that tells the story.

Greg

ptuomov

Greg, isn't the above simulation graph consistent with your theory? At 6000 rpm and with S3 cams, the stock intake port reverses in simulations. That's not ramming anything, at least not in the right direction! ;-)

I talked to my head guy just now and he said that when he flowed the stock 4V .4R heads with warts and all, his first thought was "holy ****!" I interpret that as the stock heads already flowing pretty well. ;-) What Dennis needs for his 5.0 Screamer motor is a new intake manifold or ITB, and let his engine rev _all_ _the_ _way_!

Now, this is all pretty off topic for Dennis's thread, but that's his cross the bear for having the best 5.0 engine and the most popular on-topic thread on RL69.

mark kibort

Yep, thats what we alll get if we follow the math. So, the BMW not being so special, gets 208psi? In fact, the newer models make even more than that! Get this, some get over 340rwhp, or near 400flywheel hp out of a 3.2. anyway you slice it, its way way over 200psi. I guess the question Im asking would be, is this engine that special and if not, it makes sense that Dennis can make 375rwhp, which is over 420 at the flywheel. coincidentially enough, that is the lower displacement 2.8 liters, (171ci) that the "formula" calls a high chance of "BS factor" when they were talking about a then engine making 170ft-lbs of torque at 5000rpm. pretty close to the same as this curve.

I do think there are a lot of wishful numbers attached to some motors, but there quite a few these days with some astounding values with not much in the way of modifications.

mk

dcrasta

Wow I play this clip through my 5.1 surround . Awesome.. Would make a wicked ring-tone or timer alarm. [couldn't resist]ringtone

beentherebaby

Accurate engine dyno testing, I emphasize "accurate" and "engine" dyno testing separates theory from reality. There are many factors involved that effect the results including the accuracy and operation of the dyno.

The engine dyno doesn't lie - when it's properly calibrated and operated.

FWIW- BMEP is typically used to compare peak torque output of an engine not peak HP which can vary considerably based on the peak RPM and tuning.

Chuck Schreiber

Dennis,
Hows the motor holding Up?
Would really like to do cams. I'm guessing that the S3's are still realitivly accessable??