More boost = more HP ???

[valmes]

Look at the examples bellow... two different ways of achieving same BHP numbers. AFR stays constant at WOT and timing is prefect , did you spot the differences?

Ver. #1

CC: 2500
CYL: 6
MAX RPM: 7400
BOOST BAR: 2.5
AFR: 11.8
AIR TEMP (C): 25
UNDER BONNET TEMP (C): 47
ATMO PRESSURE (C): 14.7
VE (%): 85
TURBO EFF. (%): 68
INTERCOOLER EFF. (%): 65
PRESSURE LOSS (PSI): 3
FUEL RAIL PRES. (PSI): 43.5
AFPR RATIO 1: 1
INJECTORS (cc): 600

TURBO OUTLET AIR TEMP.(C): 246.75
I/COOLER OUTLET AIR TEMP.(C): 102.61
CFM ON INTAKE: 971.43
AIR MASS (lb/hr): 3432.08
AIR MASS (lb/min): 57.20
CFM FOR EACH TURBO: 485.72
CFM OF EXHAUST GASES: 680
AIR DENSITY (g/CF): 26.61
DENSITY RATIO: 3.5

SINGLE INTAKE DIAMETR (mm): 82.49
TWIN INTAKE DIAMETR (mmX2): 58.33
SINGLE EXHAUST DIAMETR (mm): 69.01
TWIN EXHAUST DIAMETR (mmX2): 48.8

MAX FUEL RAIL PRESSURE (PSI): 80.25
FUEL NEEDED (cc/min): 3056.88
MIN. FUEL PUMP FLOW (lph): 229.27
FUEL PUMP REQ. BY INJ. (lph): 216
RECOMENDED INJ. SIZE (cc/min): 636.85
FP ADJ. INJ. SIZE (cc/min): 600
INJ DUTY CYCLE (%): 0.85

CRANK HP (BHP): 581.71
WHEEL HP (WHP): 485.35


Ver. #2

CC: 2500
CYL: 6
MAX RPM: 8500
BOOST BAR: 1.2
AFR: 11.8
AIR TEMP (C): 25
UNDER BONNET TEMP (C): 30
ATMO PRESSURE (C): 14.7
VE (%): 100
TURBO EFF. (%): 78
INTERCOOLER EFF. (%): 80
PRESSURE LOSS (PSI): 1.5
FUEL RAIL PRES. (PSI): 55
AFPR RATIO 1: 1
INJECTORS (cc): 530

TURBO OUTLET AIR TEMP.(C): 129.78
I/COOLER OUTLET AIR TEMP.(C): 45.96
CFM ON INTAKE: 825.16
AIR MASS (lb/hr): 3433.48
AIR MASS (lb/min): 57.22
CFM FOR EACH TURBO: 412.58
CFM OF EXHAUST GASES: 577.61
AIR DENSITY (g/CF): 31.34
DENSITY RATIO: 2.2

SINGLE INTAKE DIAMETR (mm): 76.03
TWIN INTAKE DIAMETR (mmX2): 53.76
SINGLE EXHAUST DIAMETR (mm): 63.61
TWIN EXHAUST DIAMETR (mmX2): 44.98

MAX FUEL RAIL PRESSURE (PSI): 72.64
FUEL NEEDED (cc/min): 3058.12
MIN. FUEL PUMP FLOW (lph): 257.9
FUEL PUMP REQ. BY INJ. (lph): 241.24
RECOMENDED INJ. SIZE (cc/min): 716.39
FP ADJ. INJ. SIZE (cc/min): 595.95
INJ DUTY CYCLE (%): 0.86

CRANK HP (BHP): 581.94
WHEEL HP (WHP): 485.57

[Wodjno]

Smaller Intakes.. And Smaller Exhaust ??

Smaller Injectors ?

Larger back pressure ! Increased pressure in the intake at lower RPM due to less volume needed to be filled and maintained throughtout the rev range resulting in the same power at a lower PSI.. Also the air temps are so much lower as the Turbo's are not working so hard and raising the temps as high, this also increasing the density of the air at a lower flow rate. Volumetric Efficiency is spot on, also the efficiency of the intercooler is much better..

Not sure how the smaller injectors make a difference though ??


Some serious BHP there Valmes

[valmes]

Smaller Intakes.. And Smaller Exhaust ??

Smaller Injectors ?

Larger back pressure ! Increased pressure in the intake at lower RPM due to less volume needed to be filled and maintained throughtout the rev range resulting in the same power at a lower PSI.. Also the air temps are so much lower as the Turbo's are not working so hard and raising the temps as high, this also increasing the density of the air at a lower flow rate. Volumetric Efficiency is spot on, also the efficiency of the intercooler is much better..

What AFR's where you running at WOT ??

Some serious BHP there Valmes

Sorry, I wasn't clear... it's just an example. I am certainly aiming at ver.2 as much of my setup is going in that exact direction. I love how my car is pulling right now and I guess out of boredom and anticipation before Sep. 2 doing some bench racing and thinking Decided to share some of it with those who are interested. Since we don't have any Dynos around here and Apexi RSM is nothing to call precise (I retract my statement here... we checked it against electronic measurement equipment we use on local Drag Events... and its right on... +/- 0,01%) , I hope I can make some assumptions of power levels on Sep. 2 when I run the 1/4 mile on local "dragstrip" .

I will make videos and EMU logs of the runs... I do hope to overshoot the 400 bhp mark at least. Although calculations suggest there is a "theoretical" potential to get up to 450WHP(550BHP) out of this setup! Will see how it goes and then will decide on what to improve to get where I want to!

PS: It's kinda of backwards, but I will know how efficient my car is from what boost at what traps and ETs it will run.

[Wodjno]

Sorry, I wasn't clear... it's just an example. I am certainly aiming at ver.2 as much of my setup is going in that exact direction. I love how my car is pulling right now and I guess out of boredom and anticipation before Sep. 2 doing some bench racing and thinking Decided to share some of it with those who are interested. Since we don't have any Dynos around here and Apexi RSM is nothing to call precise, I hope I can make some assumptions of power levels on Sep. 2 when I run the 1/4 mile on local "dragstrip" .

I will make videos and EMU logs of the runs... I do hope to overshoot the 400 bhp mark at least. Although calculations suggest there is a "theoretical" potential to get up to 450WHP(550BHP) out of this setup! Will see how it goes and then will decide on what to improve to get where I want to!

PS: It's kinda of backwards, but I will know how efficient my car is from what boost at what traps and ETs it will run.

So are my interpretations the way you expect thingc to work ??

What difference would the smaller injectors make for increased power ??

[Nick Mann]

It's all down to mass of air entering the cylinder. But by those calculations it appears that although the pressure has doubled, so has the temperature. So the mass has stayed nearly the same.

Would there be a point in the middle where the extra pressure did not give a massive increase in the air temperature? Then surely a higher mass of air could reach the cylinders?

Either that or some serious intercooler work!

[valmes]

What difference would the smaller injectors make for increased power ??

They will be adequate to the needs...

Most people consider going Bigger is always Better... not.

First of all bigger injectors will require some fuel corrections to run properly. Most will alter the airflow signal to get where they want with AFRs, but it will affect your timing maps as well. Atomization at higher pressure will be better, but you are correct it will not affect HP in a major way. But why bother if correct size can cover up to the limits of turbos and fuel pump? One more thing bigger is almost always costs more...

I've seen people who ran 800cc-1000cc producing only 400 or so bhp...

Sizing matters... Compressor turbo maps show where they would be most effective. Intercooler doesn't have to be too big to be a good compromise between cooling efficiency and pressure loss. Bigger pipes are not always better... and so on.

[valmes]

What I meant to show was that: cooling efficiency, turbo efficiency, volumetric efficiency are as important, if not more important than simply upping the boost.

Would there be a point in the middle where the extra pressure did not give a massive increase in the air temperature? Then surely a higher mass of air could reach the cylinders?

Just increase efficinces in those areas and you will get 875BHP/760WHP from same boost level (2,5 bar)... although your requirments will rise too! 660cfm for each of two turbos or single 1320 cfm monster! Single intake diametr of 100mm (up to throttle body), exhaust of min 80 mm, 960-1000cc injectors, twin walbro 255lph fuel pumps. At that displasement it will require all measures to be taken to avoid knock... racing fuel, engine built to withstand such loads... and tranny to compliment such engine... that's why I would prefer to run less boost on my engine!

[bradc]

Very interesting valmes, I assume the single/dual intake and exhaust refers to either a single or a twin throttle body and exhaust exits.

What effect would replacement cams have on a setup like that? Is that where you're hoping to increase the engine volumetric efficiency?

Also what happens if on the second example you drop the redline back down to 7400rpm, how much power do you lose?

[valmes]

Very interesting valmes, I assume the single/dual intake and exhaust refers to either a single or a twin throttle body and exhaust exits.

What effect would replacement cams have on a setup like that? Is that where you're hoping to increase the engine volumetric efficiency?

Also what happens if on the second example you drop the redline back down to 7400rpm, how much power do you lose?

With stock max HP at 5500 and redline at 7400 -----> 507BHP/415WHP

[Paul C]

How can we put the calculated figures into practice or is it a game of trial and error.Is there a list of known mods that will drop us into those required calculations?What are the efficencies of the stock setup?

[valmes]

Didn't go too well... at least not as planned.

I came to the dragstrip, poured 20 liters of 106 octane gasoline and decided to go in steps, raising boost each time.

First run, terrible start from 4500 resulted in car bogging down. Missed the 3rd gear too. I think I have a bad syncro there that needs to be changed.

Max boost at 0,77 bar - 13,46 sec. I thought something was weird, since car wasn't making full power up top in fact it felt like detonation was coming out of nowhere! I knew my adjustments were on the rich (sometimes even under 10:1) side + low boost + 106 octane! Something was seriously wrong! Then I noticed my real AFRs at 17:1 at 7000 rpm (Oh my...!!!) and fuel pressure dropping to almost 1,5 bar (from more than 4) under boost ... Fuel pump!!!

After quick inspection it was clear the Walbro fuel pump has died on me... and the closest place to get a new one is at least 200 km away!

Well, bad luck again I guess...

On the bright side, the second Legnum VR-4 ran incredibly well, even though on stock turbos, injectors and fuel pump. List of mods is quite short - EVO8 Ogura twin plate metalaceramic clutch, HKS SSQV, APEXI S-AFCII, APEXI AVC-R, full 3 inch de-cated exhaust, K&N filter...

Boost at 1 bar, leaner fuel. Start from 7400 RPM with clutch dump. On first 4 passes it ran 13.3-13.5... and since track was still available for free runs we decided to check against other cars.

First on the list was Mercedes Benz E55AMG (with only 354 BHP). It was far behind the Legnum on the finish line! By far I mean at least 4-5 car lengths from what I saw. The owner went “It can’t be for real… lets try again!” Second time same result!

Then he asked his buddy on 2006 BMW M6 (507 BHP) to try it against "That" ... You should've seen their faces! One with evil grin, expecting something interesting, and the other one stumbled and going "Huh? That?!? Are you pulling my leg or something?"... 10 mints later... Legnum is one body length ahead of 2006 BMW M6 at the finish line! Second ran against the BMW resulted in the same scenario. Legnum won again!

[bradc]

Not good to hear about the walbro, hopefully 17:1 didn't do any damage. Are you intending to tune it to about 12:1 eventually?

As for the other results, I can only laugh, I guess the VR-4 got more traction off the line and held out for the win?

[valmes]

Not good to hear about the walbro, hopefully 17:1 didn't do any damage. Are you intending to tune it to about 12:1 eventually?

As for the other results, I can only laugh, I guess the VR-4 got more traction off the line and held out for the win?

I did get home off boost on the same engine... so I will have to check compression to make sure engine is alive, but I do hope for the best.

Of course I will be trying to get it back in shape. New fuel pump, probably new AFPR... I know the power is there!

[Louis]

Hang in there, good luck

[valmes]

Thanks Louis, I will!

[EdmundVR4]

Hope everything is OK, Valmes.
I had a Walbro pump fail on me about 6 months ago. In my case the pump became noisier gradually & i had it replaced. Wideband AFR is realy useful when pushing the limits of any car!

[valmes]

Everything seems to be fine... with the engine.
Will have to take off the gearbox though... some strange noises are coming out of it .

[valmes]

I think I've nailed my problem...

Whenever I tried to up the boost I got my AFR screwed up. It would go richer and richer with RPMs. While I was getting CEL (from EMU cutting into injector wires) I thought stock ECU somehow dumps all the fuel it can, since its thinking something is wrong and tries to play it safe... but then Greddy injector adapter came and CEL code is not an issue any more... What is it? Stock lambda sensor interfering with open loop EMU corrections?

I finally got it when my fuel pump died - A/F ratio was fluctuating so rapidly with fuel pressure change and car would at first struggle, then pull hard, when it leaned out, but as it leans out even more, the torque disappears...

It has to be fuel pressure!

My self-made AFPR is probably rising rate not 1:1, as I previously thought!
I just never got a chance to log voltage with EMU and compare the "boost" curve with how my fuel pressure behaves. I looked at the FP gauge and from what I could see everything was ok. You can't really do that, that just shows how important is datalogging!

There are two ways of overcoming this problem...
Getting good AFPR with 1:1 rate or creating fuel maps in e-manage that will deal with this issue.

I just thought I would share in case somebody is ever stuck in the same situation...

[valmes]

Video: 2006 BMW M6 vs. 1997 Legnum VR-4 (Twin TD03... stock turbos):

BMW stock 507bhp from the factory.

Mitsubishi Legnum VR-4 - 2,5L V6 (6a13) DOHC Twin Turbo, stock FMIC, 5MT with Ogura twin plate metalaceramic EVO8 clutch and flywheel. Decated exhaust 76 mm (3 inch). Apexi AVC-R and Apexi S-AFCII. Stock downpipes, heads, turbos and mostly everything else... boost set at ~ 1bar (14,7-15 psi)

[Paul C]

Is the legnum modified and was the m6 in sports mode. I would of expected the m6 to thrash the legnum it must have about 500bhp. good show by the vr4. Is the m6 just starting to catch up at the end?