Disappointed Dyno

[Lextreme II]

I took my car to a local dyno center. They use Mustang Dyno machine and we made few 4-5k rpm runs and we hit 24 psi at around 4.5k. I was using an Electronic Boost Controller but it wasnt working properly. So i disconnected and went manual with a build 1 bar spring. However we managed to achieve about 12.00 psi.

The worst thing is not the boost, but the result. The result was very disappointing and perhaps you guys can tell me why my car was dyno such low number.

According to the dyno sheet:

Boost: 12.00 psi
rwhp: 236
TQ: 280
AFR: from 12.7s to 10.4

There are couple of reasons i think the result is low.

1. Restrictive stock pipes. I use stock Y pipe back to silent the noise because its a street car. I had dual 3" and hated it.

2. AFR 10.4 is too rich and will hinder power

3. Somthing is wrong with my engine?

4. Possible Dyno or Techician.

What do u think?

LS400T Dyno Sheet

 

[Lextreme II]

Here is the dyno sheet....

 

[cowboy bebop]

Sweet motha' that's a bad pull right there. The curve looks all over the place and power is WAY down. Stock 2jz-gte's make between 280 and 300rwhp at 11psi, stock twins.

The curves are noticably jagged so much more tuning is needed. 10.4 : 1 a/f is rich, but not enough to stifle power all that much on boost. Possibly the stock Y pipe is holding it back, but it should still be making much more than that.

Eric

 

[Pro]

are you running the stock computer David?

that's a horrible looking graph.

 

[Lextreme II]

are you running the stock computer David? that's a horrible looking graph.

No I am running a piggyback called Split Second FTC1

 

[Eels4Ever]

I would look into better tuning of the fuel computer. Make sure your using a wideband 02 sensor or another high quality sensor (makes datalogging easier, fouled 02 sensor will also help run rich). I do not know if your setup has a "knock sensor" but if the car was knocking or "fuelcutting" and pulling timing that may be the reason. If you are only making 12lbs on a 1bar (14.7psi right?) spring you may be leaking boost (ic/plumbing), generally you will spike at least 16-17 even if ur only averagin 14.7, compared to the 12 that ur car "spiked". The turbocharger would have to be grossly mismatched to not be able to spool over that much of the rev range. Restrictive (small diamater) exhaust will also tend to give you alot more low end torque and alot less high end horsepower. Got any more graphs? (Im not used to seeing in MPH compared to by RPM (mb a US thing?)

 

[rdm20fan]

Hey David, sorry about the low numbers.
My AFR was also low-mid 10's. Chris wanted to keep it safer, so I don't think your problem is fuel. It could be better, but your not loosing 200RWHP from it.

Are you using a different head/piston combo, and have resulted in a very low compression?
12 psi on the stock motor should be over 400RW Chris and I were 370 at 7-8PSI.
12 psi at the manifold from a 15 spring is probably correct. the pressure loss of 3psi after an intercooler is good.

are you running stock timming? I was.
what was done to the motor. stock?/rebuilt? what did you change, and keep the same if rebuilt.
Don't worry, you'll get it!
My previous #'s 5psi 321; 7-8psi 371were also on a Mustang dyno. stock pistons
the #'s after the rebuild are on a Dynojet. 18psi 510 8.5:1 pistons. My dyno graphs were very choppy also. yours graphs look simular to mine, just lower #'s. I also need to spend more time tunning.

 

[rdm20fan]

not as choppy, but close.



The second small graph is the 370RW at 8psi on the stock pistons. the AFR was all over the place

If I remember correctly they smothed out the graphs a little. I think they looked more like yours when first made.

 

[Lextreme II]

are you running stock timming?
I was what was done to the motor.
Don't worry, you'll get it!
I also need to spend more time tunning.

I am retarding 1 degree per lb of boost. Perhaps i am retarding too much. We didnt have a chance to do any tuning. The motor has forged Ross 8.5:1 pistons with forged rods and ARP all over along with some head work. This engine boosting 24 psi (the needle was hitting the stopper on the gauge) without any problem. I would say a combinations of the above gave me low numbers. I think tunning play about 90% of it.

 

[cowboy bebop]

Are you on 1uz heads, or 2uz heads? An what are your cam profiles? One more thing to looks at is to find a Dyno Jet, and steer away from the Mustang Dyno. The Dyno Jet is more or less the standard, where as the Mustang Dyno can be calibrated to read whatever HP you like by playing with the settings. It's worth a shot.

Eric

 

[rytherwr]

I, too am sorry for your disappointment. Without getting into what has already been addressed, I remember your recent post about whoopin' butt after you had fixed your battery cable and I don't think you do that on 235 whp.....I guess my question would be this....you know what the stock motor felt like (seat of the pants) and you know what the FI motor has been doing on the street and what it feels like, how did the motor sound and feel on the dyno? the same...different....???? Trying to correlate your prior performance and how it felt/sounded with what happened on the dyno....If it was reasonably the same....might be the dyno/calibration/operator etc. If it was radically different, then you head back to your engine setup, etc....to see what might have happened.


Wayne

 

[Lextreme II]

The delima is perforamance vs. noise. Right now have stock Y exhaust and love the car being streetable. The stock Y is 2.25" single and very restrictive along with a stock resonator. I would have to do a dual 2.25" with dual resonator and dual muffler would be nice......

Here is a picture of my stock setup.

 

[chrisman]

hi david,, your probably on the right track about the exhaust.. il take a look at the graph again,, but i bet the exhaust "after the turbo" is building pressure.. try and get a "dump" welded in before your complete exhaust.. and try running the car like that--i know it may seem alot louder--but it sounds like music to me..
dont change anything else just yet,,but when you do,only make 1 change at a time.. and see how it feels.. then get back to the dyno.. believe me,, you will know when the car is making alot of power..

 

[chrisman]

oh yea,,, if the reason was the pressure building up after the turbo,, when you install the dump,, keep an eye on the AF.. although it was fine before,, it may lean out quickly because of the new ability to get rid of the exhaust..

 

[JamesNSC4]

First of all I think the number is a bit inacurate. I sat on David car that day and we took a spin around the block, the car pulled way too fast to get that kind of number. I think David just need to do some tuning and open up the exhaust alittle and it should clear out some problems. I know like your car quite David but you gotta scacrifice it a bit this time buddy.

 

[rdm20fan]

David I have dual 3" with 2 straight through mufflers, flowmaster 40 series mufflers , and a turbo on each side. The car is quiet. It's loader then stock, but not really loud. a lexus owner would know it, but the general public probably doesn't.
I'm sure there is HP to be gained by going to a larger exhaust, but i don't think your loosing 200WHP from the exhaust
a very restrictive exhaust would also cause the turbos to spool less quick, and not build as much boost correct.
Your not having these problems are you?
if the turbos were making 24psi, it must not be too bad.
I could only get the turbos to make 18 on my setup.

 

[Lextreme II]

I did some exhaust mod today. Deleted the 2" Y pipe and added dual 2.25" and the four stock mufflers still retained. I noticed the boost coming on slightly delay from previous but felt it has slightly more mid and top end. I will try to run this for while and if needed i will delete the two primary mufflers and see the noise level. After the Y pipe deleted, i dont noticed any increase noise at all.

Changing the Y to dual 2.25" altered some outcomes already and looking forward to do more exhaust mods before the system gets too loud. Here is how my exhaust looks like right now.. If noise is not too bad, then i will mod the exhaust like the last picture below.

 

[jibby]

That stinks!!! Best of luck getting it right...but if it pulls hard like James said maybe the dyno was innacurate... I know my Apexi fouled before, so the piggyback may be the problem if one exists....

 

[Toysrme]

David.
1) Too rich. Cap the B at 11.5. (If you want a cooler combustion chamber... That's why god intends you to install a $10 water injection system on your car, not gas!)
2) Make it a 1/2 point per psi instead of 1 point per psi. (Check for knocking & stock timing also)
3) Check & Replace the spark plugs to 2 steps colder (than stock) copper plugs, gapped down 0.05" & get use to changing them atleast once a year on a daily driver.
4) Somebody's got a little bit of boost dropping!

 

[Toysrme]

Most turbo cars can easily get away with no muffler, and just straight exhust pipe. At worst, something cheap like a straight through muffler / resonator will calm it down some. The turbine makes for some very good noise canceling.

Just a quick through for you... 12-15' of 2 1/4" - 2 1/2" galv mild steel can be had at any Lowes / Home Depot for $12-15 disguized at EMT Conduit, and "fence posts". All the good stuff is normally in the home & garden centers outside. Hey... It's the fastest, cheapest way to test it!

Y-pipes... Do very little to noise. Noise is a factor of resonation, muffling, and exhaust length. Most of the time, merge pipes don't really do much to any of those. (Tho some y-pipes can be "tinny" when they're too thin, or not bolted down well enough.)