How am I making this much power at so little boost

[stevieg]

Serious question, how am I making [email protected]

Relevant build information:

-7mgte 440cc injectors
-Precision Turbo Billet 6262 ball bearing, 0.58AR t4/v-band
-megasquirt AF/r is 11.4-11.8, timing is 22deg at 4krpm tapering to 20deg@7k
-Totally stock early crown majesta engine
-semi-log style manifolds 1.5" primaries->2" log->2.5" to a T4 merge collector
-38mm Precision wastegate
-Supra R154 trans
-stock upper and lower intake manifolds
-engine is entirely stock
-fuel pump is a bosch 044
-datalog shows peak dutycycle at 74% which if using a bsfc of 0.42 equates close to my uncorrected hp of 523whp
-datalog shows 186kpa max (12.4psi)
-12psi of boost only regulated by the wastegate spring, no boost controller yet
-94 octane pump gas (ron+mon/2)
-SAE J1349 correction factor

My question is not how am I making this HP as I did blueprint this build to make this HP goal but more of what did I fluke on to make this HP goal at only 12.4psi? Are these new Billet turbos just that awesome or is it my fairly agressive timing map (these engines do love timing)


here is dyno from this morning

Curious so I know what to do next time as I wasnt expecting to make this power until 16-18psi like everyone else???

steve

 

[JustenGT8]

Here's hoping this starts an informed discussion and good work putting it out there.

All boost is clearly not equal and it would be good to understand what is the other significant factor....seeing they are all related eg pressure, temp, density. it's quite a complex picture to get your head around.

A simple view would be a bigger turbo flows more air for any particular boost setting....but it's not really boost but pressure ratio that determines what a turbo will flow. Still, using a compressor map you can easily see this.

Boost at the engine though is influenced also by what the engine can flow. So the airflow of a turbo at 10psi on an unported engine may be the same as the airflow from the same turbo at 8psi on a ported engine. that makes sense to me as well.

In this instance we have 2 engines virtually identical....and i would say i have the advantage with a better designed (no offense) exhaust manifold and better fuel.

Yet the big single T makes more hp on 12psi than i'm making on 17psi....that's just too big a difference for me to grasp?

 

[stevieg]

Thanks justen, exactly the kind of replies I'm looking for. I'm constantly explaining to less-knowledgeable people who always immediately ask what psi I'm running as if it's going to tell them exactly how much HP I'm running.

Bigger turbo at same psi as smaller one will make more HP as it's Flow@psi and not just psi. For example my 62mm compressor on my engine makes 573whp@12psi and my buddy's 572 bigblock mopar w/118mm turbo makes 1500whp@12psi, another way to look is increase of HP over N/A.

My engine makes ~250whp n/a or an increase of 323hp, my buddy's makes 700ish n/a or an increase of 800hp at the same boost level

And that's not even accounting for differences in the new compressor wheel designs boosting efficiency on my turbo over my buddies.

Now turbo sizes aside what does your timing map look like? How much timing are you running at 12/17psi at say 6,000rpm?

Steve

 

[JustenGT8]

My ign adv tops out around 18 deg at peak loads...we know it'll take more but i'm keen on preserving the engine as i do more circuit events than short drag runs.

Mine makes very close to double the stock n/a power at 1bar which is what you would expect......yours blows that out of the water, which is kinda amazing really?

 

[stevieg]

My ign adv tops out around 18 deg at peak loads...we know it'll take more but i'm keen on preserving the engine as i do more circuit events than short drag runs.

Mine makes very close to double the stock n/a power at 1bar which is what you would expect......yours blows that out of the water, which is kinda amazing really?

whats your ignition advance at say 160/180/200kpa and 4,000/5500/7000rpm?

I'm actually serious about trying to figure out whats going on cause in my head I think the dyno is wrong but at the same time I dyno'd with the automatic trans and 8psi with a max of 424hp/450ft-lbs

dyno is a dynocom and we used SAE J1349 correction factor

steve

 

[8pack]

You can always get a dyno run elsewhere if you're unsure of the dyno.

Anyway, I'd say the figures seem aren't unreasonable. I'd calculate the total air flow going to the engine and compare it to proven set-ups. Yours is a great turbo too.

 

[XR8tt]

Intake air temp can change things big time...

 

[8pack]

Here's hoping this starts an informed discussion and good work putting it out there.

All boost is clearly not equal and it would be good to understand what is the other significant factor....seeing they are all related eg pressure, temp, density. it's quite a complex picture to get your head around.

A simple view would be a bigger turbo flows more air for any particular boost setting....but it's not really boost but pressure ratio that determines what a turbo will flow. Still, using a compressor map you can easily see this.

Boost at the engine though is influenced also by what the engine can flow. So the airflow of a turbo at 10psi on an unported engine may be the same as the airflow from the same turbo at 8psi on a ported engine. that makes sense to me as well.

In this instance we have 2 engines virtually identical....and i would say i have the advantage with a better designed (no offense) exhaust manifold and better fuel.

Yet the big single T makes more hp on 12psi than i'm making on 17psi....that's just too big a difference for me to grasp?

What turbo were you running?

 

[JBrady]

Obviously your combo is making GREAT power.

That said is the numbers shown on your dyno sheet comparable to say JustenGT8s ? Since Justen has/had the best results posted for a stock assembly until you posted this. Both of you have an excellent grasp of the variables so this discussion is extremely (lextremely?) interesting.

First question: What is the CF shown at the bottom of the sheet. It is right before the DynoCF which I would believe to be Correction Factor. If the actual measured numbers were increased by 1.10 your numbers would be around 520rwhp.

Second question: From the link http://wahiduddin.net/calc/cf.htm it shows the SAE J1349 correction factor to possibly include an 85% efficiency or in other words an assumed 15% loss from engine accessories. IMO it is better to use ACTUAL measured performance as turbosupercharged engines include turbo and intercooler efficiencies that may not equally correlate to a comparable NA engine as the wastegate will compensate for atmospheric pressure differentials.

So, if your numbers were increased by 15% and/or possibly another 10% your dyno numbers would not be comparable to an uncorrected (true as measured for the day and conditions) dyno.

Regardless, excellent results. I would recommend getting some uncorrected data AND doing some on road/track performance testing to measure how much power is available for actual use. Nobody races a correction factor.

 

[stevieg]

Ya I'm not 100% clear on that 15% thing in the sae j1349 standard but it's supposed to be corrected to a specific barometric, density, temperature set if variable and is supposed to be what all new vehicles etc are tested to.

The uncorrected numbers are 523whp/547ft-lbs which is pretty close to what my trap speeds should be when factoring in 130mph, 2600lbs and cylinder1 was only 75psi compression and not really contributing much.

Also I'm 3000ft above sealevel

Steve

 

[stevieg]

As for actual testing I'll have to wait till spring time now as anything more than 5% throttle in gears 1 through 4 at any speed just blows the tires off lol

 

[stevieg]

Sorry 50%, stupid not being able to edit posts lol

 

[JustenGT8]

My turbos are x2 KKK K3T. Basically a k26 turbine and K27 compressor. Each is good for 450hp @ approx 1.5 bar which seems about right.

It's not the turbo so much as what these engines will flow. They will make power with boost easy enough.

400+rwkw @ 12psi is what you see from stock LS engine with good turbo setups. That's with 30% more capacity, better flowing heads, cams and inlet manifold?

 

[FoPar]

you should really go off uncorrected or what it runs at the track mph is ur best gauge, i prefer engine dyno over chassis dyno they are usually more spot on the money. J1349 standards don't go over 10% and to be considered to have a 10% correction factor the car would need to be dynoed in 40 degree celsius heat and be in the eye of a storm. with intercoolers etc etc the car is more efficient anyway, those figures are more for aspro cars. if u made 420 on 8psi auto, going manual is a pickup of 30-40rwhp plus the extra 4psi easily helps get to 520

being bigger doesn't necessarily mean it will make more power. on the brothers 2JZ wen't from a GT42 76mm 1000hp 1.06 A/R turbo to a 1200hp 80mm 1.32 A/R turbo they produced the same power till 32psi then the 80mm came into its efficiency. again on a mates 1JZ went from 550hp GT35/40 62mm T3 .69 A/R to a 850hp 67mm Precision billet CEA 6765 T4 .6 A/R pound for pound and hp to hp all the way to 25psi exactly the same as the 35/40. the only difference is the boost came on 500rpm later with the 6765

however, in the 1UZ a change from .6 A/R to a 1.0 A/R showed a 70rwhp gain. less backpressure and the turbo's were no longer choking.

to run a 130mph in a 2600lb car u only need 420hp @ the flywheel. we ran that mph in a 3100lb car that only made just on 500hp @ the engine.