Your Mass Air G/S?

[Jchouin1]

I'm curious about the g/s numbers for the bigger turbo cars just for comparison purposes. This is cut/paste from a log of mine to make is easy to read. I have been attempting to schedule dyno time at 3 different shops, all were fairly booked up until the end of the month due to saturday being my only available day of the week to go, but I'll try to get a few pulls soon. My last dyno was on stock turbo, stock exmani, stock dp with all other bolt ons, and it made 291whp on a dynojet @ 20psi with approx 250-255 g/s. What are you guys flowing?

[BrianZX10R]

my car dynoed 383 with 308 grams a second at 20.88 psi. at 21.5 i was at 325 grams a second. what turbo are u running that u are getting 335 grams second?

if your grams a second are in any way shape or form related to mine u should be at 400 whp no doubt. and about 380 wtq +

[manelscout4life]

op has atp2871r how does he get more g's then some1 with a bigger turbo?

[ToledoSpeed3]

Originally Posted by manelscout4life op has atp2871r how does he get more g's then some1 with a bigger turbo?

Temp and wot maf calibration would play a role in accuracy and comparison of reported numbers. It's not an apples to apples comparison, yet it is interesting to see what folks report.

[manelscout4life]

brian didnt u get tuned before the load cap fix? so chances are your maf was scaled down so thats why u show less g's

[madvillain]

Ill try and get some numbers for you tomorrow man!

[zx2man]

at 17 psi stock turbo, I made 291 whp myself, and my g/s was around 260.

Sidenote: Just got email back from Brandon@Surgeline, and he says I should get a Big Maf for 3071 atp @ 18-19 psi. But if Brian is doing fine with his Cobb intake, I think I should be good too. I "thought" if you wanted 400 and more whp, you needed to go big maf??

[rodrigo]

from what limited knowledge i have.... i could have sworn that maf flow could be altered when adjusting maf calibration scales....

therefore making one comparison from one guy to the next possibly flawed....

maf voltage on the other hand would be more uniform across....

ehh??

[SSinstaller]

Can't read the g/s on my 3.25" MAF, but 22psi ~6000rpm is 4.4v from the sensor... I think that means I have eleventy billion hp...

[BrianZX10R]

GT3076 with cobb intake at 21 psi was 4.7 V

[rodrigo]

batt car on measures like 13.2 volts... pretty good no?

[zx2man]

Lenny, your not going big maf right? I know you got the cp-e inlet for that 4inch opening. And Brian your running cobb intake&maf for yuor 380 whp 3076 setup, Dont know why I would need a big maf for 18-19 psi 3071 atp setup.

[rodrigo]

no big maf.....

and bigger maf will also increase the chance of creep since it will allow more air in.....and the snowball begins

so stock maf is a ok

[Lex]

Yes, g/s correlate to whp - but your calibration has to be correct. In other words your WOT commanded AFR must match actual AFR with LTFTs close to 0%.

[cld12pk2go]

Originally Posted by Lex Yes, g/s correlate to whp - but your calibration has to be correct. In other words your WOT commanded AFR must match actual AFR with LTFTs close to 0%.

Yep, and meth injection will skew things as well...

[cld12pk2go]

FYI,

The 335 g/s equates to 44 lbs/min massflow, which is just inside the GT2871's (56 trim) compressor map. It can do this at around 68% adiabatic efficiency (very good) at a 2.5 pressure ratio.

With a little overspinning, it can probably support that at around 2.75 pressure ratio as well at a similar efficiency.

[Lex]

And according to this K04 Compressor map, we don't want to be too far from 0.22-0.23 m^3/s flow or we're overspinning the little guy.

That lines up with around 250g/s-260g/s at 2.4 pressure ratio which is ~20psi at sea level.

[cld12pk2go]

Originally Posted by Lex And according to this K04 Compressor map, we don't want to be too far from 0.22-0.23 m^3/s flow or we're overspinning the little guy. That lines up with around 250g/s-260g/s at 2.4 pressure ratio which is ~20psi at sea level. Are you assuming any pressure drop in the air intake to the turbo? I typically assume 0.5 PSI drop there which results in 2.5 PR for 20 PSI at sealevel with 1 PSI loss assumed across the IC.

I wonder what density of air they assume in that m^3/s units of flow? Looks like the K04 tops out around 0.23 m^3/s. Assuming STP that should be 230 L/s of flow at 1.298 g/L or about 298 g/s capability (seems in the ball park, but a little on the high side since I typically only get ~270 g/s and should be overspinning mine)...

Ah, it is in the fine print. Looks like their reference is 100,000 Pa (1000hPa) and 25°C (298K). Air has a density of 1.168 g/L at those conditions.

This works out to 230 L/s* 1.168 g/L = 268 g/s flow potential. This is pretty close to my max flow around 25°C ambient conditions. I can get around 270 g/s overspinning a little, or a little over 300 g/s when it is -10°C outside.

[Ziggo]

For the pressure ratio you need to include the pressure drop across the intercooler also. .68psi for the Cobb FMIC.

[Lex]

I see something in the 260 g/s range at 25 degrees with 18-19psi measured at the manifold. So that falls in line with the map.

The GT28 you posted has the ability to outflow the K04 by around 10-11 lb/min since the K04 map stops at around 34lb/min. If 260 g/s ~300whp we are talking about the GT28 being able to support somewhere in the 380-390whp range.

cldpack, is that GT28 compressor the same used in the BNR stage 3 turbos?

[cld12pk2go]

Originally Posted by Lex I see something in the 260 g/s range at 25 degrees with 18-19psi measured at the manifold. So that falls in line with the map. The GT28 you posted has the ability to outflow the K04 by around 10-11 lb/min since the K04 map stops at around 34lb/min. If 260 g/s ~300whp we are talking about the GT28 being able to support somewhere in the 380-390whp range. cldpack, is that GT28 compressor the same used in the BNR stage 3 turbos?

According to my BNR notes, the stage III has a 71mm exducer and 51.2mm inducer. This works out to (51.2/71.0)^2 = 0.52 Trim.

Here is the proper compressor map for the BNR stage III (not much different):

[aaronc7]

lets compare volts kk?? assuming stock maf size of course.

[JumpingJackson]

How much theoretical whp would a s256 be?

[cld12pk2go]

Originally Posted by JumpingJackson How much theoretical whp would a s256 be?

You can take the lbs/min flow and multiple by 9.5-10.5 to get a pretty good range for what Crank HP the turbo can support. Or just multiply by 10 if you are looking for a reasonable estimate.

Looking at that compressor map it is good for up to ~55 lbs/min, which can support ~550 crank HP.

[Ziggo]

Originally Posted by JumpingJackson How much theoretical whp would a s256 be?

My spreadsheet says: 500 crank from 5500 to 6500 assuming:
36psi @5500
33psi @6000
30psi @6500


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[MattJackson86]

Well if we are comparing volts, I hold 4.3v for a long while and peak at 4.41 on occasion...stock k04 at 18psi...

So is volts an accurate comparison? Or only if you have the same turbo?

[Ziggo]

Volts is worse than MAF g/s if you ask me. The whole reason we do maf calibration is because it varies car to car.

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[Lex]

Changes such as intake and even air filter type can skew the voltage reading of the MAF sensor. Using the AFR and LTFT data and seeing that a target AFR is met when commanded gives an extra level of confidence and accuracy to the MAF g/s reading.

[Ziggo]

FWIW I flow ~290g/s on the stock turbo with an afr of 11.0 and it resulted in 308hp. The 290g/s is pretty constant from 5000 to 6500 rpm. My actual AFR tracks my commanded perfectly.

[Lex]

No way the flow stays constant across such a broad RPM range and no way it is 290 g/s unless it's below freezing out on the stock turbo.

[Ziggo]

Originally Posted by Lex No way the flow stays constant across such a broad RPM range and no way it is 290 g/s unless it's below freezing out on the stock turbo.

I have logs of it, its about 19psi at 5000rpm tapering to 16psi at 6500. I think it lines up pretty nicely with the fact that the turbo can only flow so much. So I hit the flow limit at about 5k rpm and it the MAF stays between 285-290 for the rest of the way with the boost pressure decreasing to maintain a constant flow. Dyno and logs are at ambient temperatures 65º to 70º at sea level, not too far off from STP.

The know the actual reading of 285 to 290 is pretty suspect even though my mafcal is dialed in. My car has always run abnormally high load values so abnormally high maf values are kind of a given. My load values are above 2.1 through alot of the rev range even though my max boost is only ~19psi. I suspect that my injectors on average are flowing less than the model forcing an adjustment up of the mafcal to compensate. On the OTS map I was only boosting to 16.6psi peak for a load value of 1.92.

[bova]

my stock turbo holds from 280-290g/s from 5k-6.3k rpm and I have my maf dialed in pretty good.

[Lex]

Here's a log from today. 270 g/s in 3rd gear at ~17psi-18psi (too much traffic to do a pull in 4th) and the temp outside is 50 degrees.

[Ziggo]

A 3rd gear log from a few nights ago. I shifted at 6400, but look at the big flat spot in the MAF from about 5.2k on up @ 280-290g/s

[Lex]

Originally Posted by Ziggo A 3rd gear log from a few nights ago. I shifted at 6400, but look at the big flat spot in the MAF from about 5.2k on up @ 280-290g/s

What are your target AFRs and what was the ambient temp?

[Ziggo]

Originally Posted by Lex What are your target AFRs and what was the ambient temp?

Target AFR is 11.2 and ambient temp was ~65deg

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[driver311]

My maf gs is about 280-290 at 14psi and that was roughly 300-310whp. I took some logs today. Stock pump is holding solid at this boost. 1600-1700. Afrs were around 11.3.

[Lex]

Well Ziggo you have an overachieving system for sure.

[Ziggo]

Originally Posted by Lex Well Ziggo you have an overachieving system for sure.

I doubt it. I still only dynoed 308hp on a dynapack. I think it's far more likely that my injectors flow slightly less than the model resulting in biasing upwards of the MAF to compensate.


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[bova]

here is my log with g/s

outside temp was around 50, this was after cruising on the highway for 20min.