MSP volumetric efficiency

[Kooldino]

Is our peak VE really that bad??? Ick... but yes your calculations are correct... in theory the .8 changes with the rpm's... so you'd need to replace it per the correct value at each rpm point that you calculate..

Yup.

Based on my dyno... the torque held from 4.25K to 5K and then fell off linearly to about 6.25 k.. I lost 8% torque through that range... my AFR's were pretty stable... so in theory there is roughly an 8% drop in VE from 4.25K to 6.25K and then it droped another 10% from 6.25 to 6.75K but that could have possibly been compensated for by timing too.. timing curve affects all this.. so again it's a really hard calculation to do at all accurately.

Sure, but for calculating efficiencies on the compressor maps, I would guess that the most important thing is to use the same CFM calculations to compare both maps.

 

[Spooled]

Damn, 80% sucks. Time to buy another head and port it.

So a stock MSP head at 4500 rpm and 0.5 bar flows 189.837 CFM?

(.8 *((.07031 cubic feet x 4500 RPM) / 2)) * 1.5 = 189.837 CFM

That sounds about right. Imagine if we had a head with 100 VE at 4500 rpm... ~237.3 CFM. That would be nice.

 

[TurfBurn]

My head is full ported and reworked... so I"m maxed out.. even my intake mani and exhaust mani are ported, polished, and matched! LOL.

but yeah your math looks ok.

Later!

Steve

 

[Kooldino]

Damn, 80% sucks. Time to buy another head and port it.

So a stock MSP head at 4500 rpm and 0.5 bar flows 189.837 CFM?

(.8 *((.07031 cubic feet x 4500 RPM) / 2)) * 1.5 = 189.837 CFM

That sounds about right. Imagine if we had a head with 100 VE at 4500 rpm... ~237.3 CFM. That would be nice.

Well, don't forget that when you're boosting, you're pretty much always going to have ober 100% VE.

Since I run 17psi, I'm probably around 200%VE. Not to mention my ported intake mani and ZE intake cam.

 

[Spooled]

Well, don't forget that when you're boosting, you're pretty much always going to have ober 100% VE.

Since I run 17psi, I'm probably around 200%VE. Not to mention my ported intake mani and ZE intake cam.

Yeah, that's why I was multipliying by 1.5 (0.5 bar over atmospheric). I figured that the pressure ratio would take care of that. I don't think that the air will flow more efficiently at higher boost levels; I think it just increases the density. If it affected the flow efficiency (not VE), then it would be an exponential increase.

I guess I could have made that more clear with [0.8 VE] * [1.5 pressure ratio]

Edit: I also see that I put 100 VE as an ideal efficency for us. I guess I should have said 100 VE at atmospheric pressure.

 

[Spooled]

Kooldino, I figure that you are at 172.5% effective VE while pushing 17 psi.

((14.7 + 17) / 14.7) * 0.80

That's assuming you hit 17 psi when your head is flowing its best, and tha you don't have anything ported, etc.

 

[TurfBurn]

Yes, spooled I think is on track on this one.... VE is really a measure of the restriction to flow that the head generates... while the turbo does work to overcome this and packs air in etc... there is still a theoretical loss of efficiency due to the way flow as is indicated by the NA VE... so we can't just assume that we are erasing it by running the turbo.... you overcome it... but it's still there!

 

[Spooled]

Yes, spooled I think is on track on this one.... VE is really a measure of the restriction to flow that the head generates... while the turbo does work to overcome this and packs air in etc... there is still a theoretical loss of efficiency due to the way flow as is indicated by the NA VE... so we can't just assume that we are erasing it by running the turbo.... you overcome it... but it's still there!

Yeah, I get that there is always a restriction, but I think that retaining the 0.8 multiplier takes car of that. So basically no matter what you do, you are only flowing 80% of what you could flow with a near perfect head (IMO). I think that the effects of a good head are felt even more as boost increases. For example: if I was making 200 whp with 80% base VE and 0.5 bar boost, then I would think that I could make 250 whp with 100% base VE (all other things being ideal as far as fuel and timing). I know it sounds like a lot, but it should be correct in theory. I'm thinking that there isn't anyone around here pushing 100% base VE with an FS-DE though.

 

[Spooled]

I got 250 by adding 25% airflow increase, btw.

 

[TurfBurn]

I was agreeing with you/saying you were doing it correct

 

[Spooled]

I was agreeing with you/saying you were doing it correct

Sorry, I wasn't trying to make it sound like I was argueing. I just like to write it all out sometimes to make sure that I'm doing it right.

So what exactly have to done to the head, Turf? 3 angle, 5 angle, port, polish, VTCS, VICS, etc. I'm sure I've asked you this before, but I'm curious about a full rundown.

 

[Spooled]

This just goes to show one of the reasons that people can get so much power out of the K20a and other Hondas by slapping a turbo on them. Start with a good VE and you can make gobs of power with less boost (aside from the higher compression ratio).

On a side note, I got in touch with Coates International a while back to see what the availability of a CSRV head for the FS-DE. I know it was a long shot, but they pretty much only make them for Ford engines and motorcycles. That would be the ideal head to have! Unfortunately they put the consumer sales on the side until they get their first motorcycle out (this year) and finish up a contract they have making truck engines in Europe.

 

[TurfBurn]

Full port and polish on both sides... with matching and polishing on the respective manifolds... Ferrea necked and swirl polished stock size SuperAlloy exhaust valves.. 3 angle valve work on the intake side with polishing of the valves, and full radius (equivalent to 5+ angle) on the exhaust side valves. Also had the port passages knifedged or radiused as appropriate That in a nutshell is my 1500-2000 in headwork... Then my VICS is left open at all times, and full polishing of both halves of the manifold and the intake plenum and TB opening as well...

 

[Spooled]

Wow, that's a lot of work. It sounds like all you need now are some custom cams. Have you played with the cam phasing to at all?

 

[TurfBurn]

No I haven't actually... I know exactly what I want to do as far as elimination of overlap and the like.. but I need to do more research and look at new cam profiles as well though... so we'll see!

 

[BradC]

I have been wondering this for a while. Has anyone that is boosted played w/adj. cam gears to dial overlap out?

 

[Kooldino]

Ok, So I made an excel spreadsheet that we can all use. It will help in turbo size selection too.

Feel free to update it yourselves, as I know it's not 100% accurate. For the VE, I either used .7 or .8, depending on the RPM. Also, as far as pressure drop goes (intercooler pressure drop), I pretty much just pulled it out of my ass.

If there are any errors other than that, just let me know.

I've also attached how my car does on a T3 60 trim compressor map.

Have fun.

 

[Kooldino]

No I haven't actually... I know exactly what I want to do as far as elimination of overlap and the like.. but I need to do more research and look at new cam profiles as well though... so we'll see!

Are you sure you want to go with a zero overlap motor? We only have 4* of overlap from the factory as is.

But if you have dyno time, get some cam gears, run them in stock formation, and then run them again with more overlap and less overlap. See what works best.

I have a feeling that you won't gain power at your boost level by going from 4 to 0 overlap, but that's just me.

 

[Spooled]

Kooldino, am I wrong in saying that it looks like your T3 is a little small for the amount of boost you are running?

 

[TurfBurn]

Are you sure you want to go with a zero overlap motor? We only have 4* of overlap from the factory as is.

But if you have dyno time, get some cam gears, run them in stock formation, and then run them again with more overlap and less overlap. See what works best.

I have a feeling that you won't gain power at your boost level by going from 4 to 0 overlap, but that's just me.

don't need inertial charging when running FI.... so you can get a slightly cleaner mixture... less chance of reversion from the exhaust gases. but it'd all be a matter of testing etc.