Harlan

iTrader: (3)

Not maintaining the same backpressure, just maintain the same power at the turbo. If you went with the same back pressure you would have a turbo with more power available, meaning it would spool faster.

I think the first version of your post where you recommended an AR size larger is probably close to where we need to be. This doesn't have to be a precise number, just having something that's within 5% either way should be good enough. I say 20% is good enough to get you there.

So you size the compressor around the mass flow rate and the efficiency you want. Size your exhaust housing 20% greater than the piston equivalent with the same mass flow.

TeamRX8

iTrader: (25)

^ old thinking that will just get you lag in return. A compressor/turbine ratio slightly more biased towards the turbine and an appropriately sized wastegate will produce a wider power curve with more total area under the curve i.e. EFR series.

Brettus

iTrader: (2)

Part of the reason for wanting to be sure on this revolves around an idea i had around wastegate setup. For it to have worked , flow through the wastegate would have to have been less than 40% of the overall flow. The discussion has changed my thinking about how vital the wastegate sizing and design really is . Most setups seem to have a really poor design given the amount of flow that has to go through them .

TeamRX8

iTrader: (25)

Yes, like the Greddy turbo. That's why a turbine wheel clip on one gains 30 hp ...

Harlan

iTrader: (3)

I went with a wastegate preferred setup, but have an EBC to make up for the shortcomings. All the rules about wastegate placement and sizing become much less important when you have a controller positioning the valve for desired pressure instead of a air signal against a spring. At that point the only thing that matters is if the wastegate can flow enough wide open to prevent overboost.

The EFR series turbos do look impressive, and if they are more efficient with higher temperatures then they should be great for us. Once I have a better handle on my sizing requirements I'll look more into them.

Brettus

iTrader: (2)

To add to this discussion :
I've been playing around with the Borg Warner software for turbo sizing . You can input rotary specific numbers WRT EGTs so it's much more useful than the Garrett one.
From this I have learned a few things .

The numbers we see on the turbine maps don't relate to the overall flow through the engine because they are 'corrected'.
They have a wastegate % prediction which is the info I wanted in the first place .

Here is one i did. Looks like watsegate is going to be just over 40%

TeamRX8

iTrader: (25)

2000*F is too high for a Renesis though maybe with that backpressure up high, but not down low

and some of the other numbers are off like boost vs rpm, an EFR in the range I think you're in should be full boost by 3000


.

Harlan

iTrader: (3)

I'd like to see the 90% Effective intercooler with a 1psid drop at that flow. It would probably be as big as the hood.

Sorry to beat a dead horse but, I still think your mass flow is high. I don't doubt you have seen readings this high, nor do I doubt that readings that high are common. What I do doubt is the MAF calibration. MAF calibration is based off the assumption that the engine is fueling a known amount. If you aren't referencing your fuel pressure on boost pressure with an external regulator then lets say it's constant 60psi.

The injector only cares about the differential pressure across the nozzle. 60psi to atm is a 60psi differential. 60psi to 2atm is a 45psi differential. Since flow across a nozzle roughly varies with the square root of the differential pressure, at 45psid the flow is 87% the flow at 60psid. If you are calibrating the maf to compensate for this instead of the injectors then you end up with 15% more airflow indicated then actual. That drags the 54lbm/min indicated number down to 47lbm/min actual, which matches what you should be flowing with a realistic IC pressure drop at 15psi out the turbo.

Brettus

iTrader: (2)

It's gunna be hard to get it exactly right because many of the numbers are guesswork .I just used the BW guideline comments . I'm hoping it's within a few % points

Adjusted EGT down a bit and changed the map ......... I wont be using an EFR Team ... they just wont fit where i want to put it .

I think the flow is more than you think Harlan ...but less than I originally thought . I'm pretty happy that those flow numbers on that example are somewhere close .

Harlan

iTrader: (3)

Without a properly calibrated flow instrument we will never know for sure. Self calibrating a MAF based on flawed assumptions only leads to more flawed assumptions. Maybe it is higher than I think, but I still haven't seen an accurate test showing that.

TeamRX8

iTrader: (25)

hen you're wasting your time calculating on the BW sites as that info only applies to which ever BW turbo model you choose

i.e. ... GIGO ...

Brettus

iTrader: (2)

Disagree . Have a play yourself and try think how the info might be valuable rather than make that assumption . Sure it's not going to be perfect , but I'm only looking for a guide . It's easy enough to make approximate crossovers for the turbines and the compressor maps don't form part of the spreadsheet so just plug your own numbers in there for those.

TeamRX8

iTrader: (25)

It's no assumption, but best wishes to whatever you decide to do.

Brettus

iTrader: (2)

. It's just as big of an assumption as my one ........ But thanks

TeamRX8

iTrader: (25)

Using that program for a different turbo means completely different spool-up, turbine and compressor maps, etc. It requires more assumptions than I can count.

I think you're getting all whacked out again over nothing. You're free to make whatever choices you want. I have an opinion that you're making a mistake. That's all.

Brettus

iTrader: (2)

Firstly , I was not trying to make any spoolup predictions and as far as that software goes , I couldn't see how you could make that prediction from it anyway . I did try manipulating the numbers out of interest BTW . If you have figured that out I would appreciate you explaining it to me ....

As for the rest of it :
It requires only one (fairly big admittedly) assumption ... and that is that the turbine flow rates of the B/W turbos are close to what I'm comparing them to . Sure that could be out by a bit , but even if it were wrong by as much as a couple of turbine steps , the results are not sufficiently skewed to be irrelevant.
The compressor maps , as i mention above, are look up and plug in . so no assumptions are made there .
The rest of the inputs are the same no matter what turbo you use so no problem there .

From there its just maths so I'm I really can't see what you are on about ?

TeamRX8

iTrader: (25)

sometimes it seems like you perceive our difference of opinions as some kind of competition between us for forum points or something

you can look up points on the compressor map, but there's a big guess where it will really be wrt the actual turbine flow. The BW site allows you to correspond them together, but it only applies to their turbos. If you want to call it one assumption then that's fine, but IMO the magnitude of the assumption is much greater than you seem to indicate

Brettus

iTrader: (2)

Not at all , more of an annoyance at your 'know it all' attitude.........
However, I do think we could have a much more measured and friendly discussion if you weren't so condescending with many of your comments.

Ok ... it just comes down to a difference of opinion then.

TeamRX8

iTrader: (25)

You're being way too sensitive.

Brettus

iTrader: (2)

Probably . There has only been one other person on here that evoked similar responses from me .... You can easily guess who that was .

TeamRX8

iTrader: (25)

I'm one if the few regular people here up to challenging you on this level. That speaks as highly to your ability as the know-it-all