1st dyno session - A little disappointed

[terminal_crazy]

Hi guys,
took my 383 Lt1 Z28 out to local dyno day.

The guys said the dyno wasn't forgiving in the numbers and everyone that came off seemed to be down on where they thought they were.

Motor
Lt1 block +0.030
Forged Scat crank/rods 11.5 cr
AFR 1101 210 LT4 heads Comp ported
Edelbrock LT4 manifold
LE spec 223/231 .610 .594 112 109 cam
42lb Fuel Injector Clinic Injectors
Mac Mid length headers (bought for original stock motor & long tubes were supposed to hang too low with lowered cars)
Moroso cai
Electric water pump
Fidanza Aluminium Flywheel
Hi flow cat & 3" exhaust
6 speed Manual
lots of other crap

Car ran awsome and didn't drop it's guts so pleased about that.

Dyno printout gives 429hp & 348.4 at the wheels.
Torque output was 360 @ 2250 and peaked 405 at 5000, dropped below 360at 6200.
I was hoping for about 480 motor & 400 at the wheels

I am limited by the cam as it just squeezes through emissions in the UK.

Fueling needs improving as it was rich starting off & leaning out up top.
1 point I noticed in the log is MAP started dropping off below 100kpi about 4k and dropped down to around 91 on all runs.
Baro was 103-104
Would this equate to a 9% drop in power ?

I've drilled big holes in the lower panel cover where the filter sits.
Where's the restriction ? Stock TB or cai?
What can I do to improve this ?
Would long tubes & duals make a big difference?

Going to track next weekend.

Thoughts and suggestions please.


TIA
Terminal Crazy

[Injuneer]

Just to clarify - on a chassis dyno, they got 348.4 HP at the rear wheels. Then they estimated flywheel HP from that? Or did I misunderstand?

What correction system did they use for air temp, barometric pressure, and humidity?

[Camaro96]

What is your total timing. What's your elevation are you running @ did you have the car tuned with all the mods. Witch cylinders are running rich

Sent from my VS996 using Tapatalk

[terminal_crazy]

Hi
That's what I understand.
They didn't hook up a tacho and the printout goes upto 6800.
My data log (EEHack) only hit 6300 on all 3 runs so not sure how accurate it is.
Transmission loss works out at 23% which seems high for amanual but gives me a bigger motor hp.

Data on printout
Dyno Dynamics Dyno Settings
BP 1021.4
RH 64
AY 21
IT 23
RR 150
TN 3.721
20030912 173954
CK 879
CF SHOOT_8
Tyre Pres std
Gear 4



3898638986


Thanks
Mitch

[terminal_crazy]

Hi

Timing is currently
RPM 95 100
400 9.0 5.0
600 9.0 5.0
800 9.0 7.0
1000 11.0 9.0
1200 16.0 13.0
1400 17.0 16.0
1600 20.0 19.0
1800 22.0 21.0
2000 25.0 22.0
2200 28.0 26.0
2400 29.0 27.0
2800 32.0 28.0
3200 34.0 31.0
3600 34.0 32.0
4000 34.0 33.0

4000 34.0 33.0
4500 35.0 34.0
5000 35.0 34.0
5500 35.0 35.0
6000 35.0 35.0
6500 35.0 35.0
7000 35.0 35.0

fueling was around 12.5 low down 13.0 in the middle then leaning out around 13.2 6k

I've not checked individual logs for knock vs fueling but across all three there were some retards so I pulled an odd degree out in a couple of places.

Tune is CL SD & runs pretty well now.
MAF is still in the inlet but from what I read, the TB is a restriction , so looking for recommends on 52mm Throttle Body.
I don't see much room over/around the top of the radiator for a better inlet than I have.


Thanks
Mitch

[Injuneer]

The pull was made at close to “standard” conditions, so which correction method (SAE or STD) isn’t an issue.

Barometric pressure - 102 kPa
Air temp - 70°F
Relative humidity - 64%

Elevation is not an issue.

The labeling on the dyno sheet is confusing. Based on the description of your mods, 429 rwHP isn’t an unreasonable expectation. But it's labeled “Flywheel Power (HP)”. Why are there two “MAX” numbers. You need to ask the dyno operator what each number represents.

If it was intended to reference flywheel vs. rear wheel, it makes no sense, because that would indicate an 18.8% drivetrain loss, which is unreasonable for an M6 drivetrain. I have both 490 flywheel HP (from an engine dyno) and 425 rear wheel HP (from a chassis dyno) = 13.3% (at the time drivetrain was McLeod Street Twin w/ steel FW, stock T56, 3” chrome moly DS, 12-bolt 3.73, 17x9.5 alloy wheels, 275/40 street tires). At 762.5 fwHP the loss dropped to 12.1%.

HP is directly proportional to MAP. HP depends on the mass (pounds) of fuel you burn. Mass of fuel depends mass of air in the cylinder. Mass of air is directly proportional to absolute pressure (MAP), and inversely proportional to absolute temperature (IAT+460). So yes, drop 9 kPa (vs. 100 kPa) and you have 9% less mass of air = 9% less HP.

If you have a stock 48mm TB, it's restricting you. While I have a 58mm TB, on the engine dyno, it showed that at max HP it was able to flow all the air required at only 77% open. Back-calculating, a 52mm TB would have been adequate, but not a 48mm.

When I took the car to the engine shop, it had a Callaway Honker intake - same as the Moroso. The guys at the shop told me to replace it, just from looking at it. That's why I went to the modified WS6 setup. The WS6 kit came with a corrugated bellows to couple the airbox to the TB (like you, I run SD). It put a bit of an offset in the flow path. I replaced it with the $6 Fernco coupling, which provided a smooth, straight, gradually transitioning from round to oval flow path. And the Holley has a built-in airfoil, compared to none in the stock TB.

The Edelbrock intake is also suspect. Dyno testing in an old magazine found that by lifting the floor of the intake to create the ”air gap” they lost plenum volume, which can hurt flow isolation to the individual runners. I have a seemingly very effectively ported GM LT4 intake, sitting on ported (210cc) GM LT4 heads. The guy that ported it (CNC Cylinder Heads, in Pinellas Park, FL) told the shop to flow the heads with the manifold. Flow improved by about 3%.

I’ll post a comparison of my build to yours (ignoring the 300-shot of nitrous) when I get more time.

As far as the issues you may be experiencing, you definitely have in intake problem. With a WS6 hood w/ baffles removed, WS6 airbox w/ topfully open, K&N panel, no MAF, Fernco 3” smooth coupling, 58mm Holley TB, I see a loss of 4 to 5 kPa at WOT/6,000+ RPM. That’s based on track data logs from my MoTeC ECU's full-time logging capability.

[Injuneer]

BUILD COMPARISON (as dyno tested while still M6)

lt1 block +0.030 - LT1 block + 0.020

Forged Scat crank/rods 11.5 cr - Forged Callies Stealth. Oliver 5.85" billet rods, 10.9 CR

AFR 1101 210 LT4 heads Comp ported - GM LT4 ported (210cc intake)

Edelbrock LT4 manifold - GM LT4 intake, 58mm throttle bores

LE spec 223/231 .610 .594 112 109 cam - 230/242 0.590/0.590 114 LSA (solid roller)

42lb Fuel Injector Clinic Injectors - 74 #/HR (@58 PSI) Bosch (sized for 300 dry shot)

Mac Mid length headers - AS&M 1-3/4" single cat mid-length, left collector modified to point straight back

Moroso cai - WS6 hood/airbox, all baffles removed

Electric water pump - stock gear driven water pump

Fidanza Aluminium Flywheel - was McLeod Street Twin, steel flywheel

Hi flow cat & 3" exhaust - 3" Y branches w/ dual 3" Carsound cats into 4" Mufflex catback

6 speed Manual - 6 speed manual


Build goes back to 2000, explaining some of the parts like the heads.... not much else available back then.

Odd cam specs due to - nitrous, ability to meet NJ tailpipe emissions, while running NA does not justify the solid roller, but on spray, redline is 7,200 RPM.

Tune is open loop, speed density, no knock sensor. Car was tuned NA on Sunoco 94-octane, which is no longer available.

Keep in mind, things like the BME nitrous pistons tend to eat HP, because of the heavy crown, ring clearances, and the poorer stabilization (rock) with the ring pack dropped lower.

As noted in earlier post, NA flywheel HP on an engine dyno, was 490 HP on 94 octane. To baseline the nitrous tuning, it was run on VP Fuels C16, and bumped it to 496 at the flywheel, w/ no changes to the tune. When the engine was installed in the car, the chassis dyno showed 425 rwHP. Interesting info.... same setup, but with the TH400 and a non-locking converter, rwHP dropped to 370, 20.1% loss for the TH400 vs. 13.3% for the T56. Eventually we bumped the nitrous up enough to make 800 HP/800 LB-FT at the flywheel. TH400 losses jumped up to about 22.5%, netting only 620 HP at the rear wheels.

What diameter are the Mac primaries? I ran JBA 1-5/8" single cat headers on the car when it was mostly stock, and they did nothing at all for peak HP.... really seemed to choke the engine.

[terminal_crazy]

It was an open dyno day, so the guys were busy all strapping cars down, easy did 25+ cars whilst we were there.
I did ask about the 2 hp figures. Answer: Dyno reads the power at the roller and back calculates the crank hp?
430 crank is ok but that makes the rwhp figure low. I’ll try contacting them and get back.

Throttle body is an easy upgrade. Ditching the maf is ok as car runs ok now on the SD tune.
Long tubes and duals I think would help but too costly just at the moment.
I have unused NOS kit but i see traction/axle issues in that future, a spare axle needed 1st so i can do gears.

I presume 10% gear increase helps with the dyno figures. (Increase in torque)... still don’t know how they’d know the rpm.

I’m in England so shipping parts out isn’t cheap so I don’t see a lid in the near future.
Will have to google intake mods.

I’m at an 1/8 mile track on Saturday. First time in 20+ years
See what she does.

Thanks Fred, most helpful.

Mitch

[terminal_crazy]

The Macs i think are 1 5/8. They were great on the stock motor and ceramic coated.
I have a mate that bends bike pipes. I can make stainless headers and exhaust but not sure on the heat they will dump out.

Thanks
Mitch

[Fastbird]

If you have MAC headers, they are indeed 1 5/8 and you are certainly leaving power on the table.

But......I'm confused. If your TQ peaked at 405, then that is your peak TQ. So 429/405. That actually pretty solid for that small of a camshaft. That power curve is beautiful. You have a PERFECT ripping around the street machine IMO.

[Injuneer]

If you have MAC headers, they are indeed 1 5/8 and you are certainly leaving power on the table.

But......I'm confused. If your TQ peaked at 405, then that is your peak TQ. So 429/405. That actually pretty solid for that small of a camshaft. That power curve is beautiful. You have a PERFECT ripping around the street machine IMO.

The problem is the graph shows FLYWHEEL HP. How do you measure FW HP on a chassis dyno. They told him they measure rwHP, then back-calculate FW HP. With that explanation, nothing makes any sense at all.

[terminal_crazy]

Hi
Reply from the Dyno guys:

The lower of the two readouts is the wheel HP, the higher of the two is flywheel HP.

The other plotted line is indeed torque, which is at the flywheel.


... so that clears that up then!
Thanks

Mitch

[Injuneer]

Doesn’t really clear it up. Those numbers represent a driveline loss of 18.8%

He had to start with the 348.4 HP he measured at the rear wheels. The flywheel HP has to be calculated based on an ASSUMPTION of drivetrain loss. Maybe he somehow started with torque at the rear wheels, and backed into torque at the flywheel, then calculated flywheel HP, but it requires an accurate engine RPM. Seems more likely he started with wheel HP, divided by 1 minus the ASSUMED drivetrain loss, and the program calculated the flywheel torque from the ASSUMED flywheel HP.

Note that drivetrain loss is calculated by dividing the difference between flywheel HP and wheel HP by the flywheel HP, not the way you did it to get 23.1%.

429.0 - 348.4 = 80.6

80.6 / 429.0 = 0.188 = 18.8% loss

Might be close for an auto trans, but with the T56 I would use 13.5% at your HP level - see the next to last paragraph in post #7.

348.4 / ( 1.000 - 0.135) = 348.4 / 0.865 = 403 flywheel HP.

You indicate he didn’t actually measure RPM of the engine. Did he ask for the rear axle ratio? Because he can’t derive engine RPM from the dyno drum RPM without the rear axle ratio and the tire rolling radius (and that changes during the pull). Are you sure he didn’t clip an inductive pickup to one of your plug wires? Could the data RR 150 possibly indicate he ASSUMED a tire radius is 15”? Could TN 3.721 be the ASSUMED axle ratio?

Where did you get the A/F ratio numbers? Typical sweet spot fo peak torque and HP is generally between 12.8-13.3:1. So it’s not necessarily leaning out excessively.

Maybe it’s a moot point, because either way you need to find out why the engine is making 70 to 95 HP less than the core elements indicate it should be making. Several of the items already suggested need to be improved.

[terminal_crazy]

Thanks Fred,
Nope, no tach pickup fitted. I'm pretty certain they attached one to the previous car which is why I quiried it.
Never asked for gear sizes/tyre sizes or anything else. I just said 4th is 1:1
RPM: Dyno chart prints out to 6850. I had Steveo's EEHack running on the laptop so it connects & logs when the ignition powers the PCM to communicate.
All three runs revved out at 6144,6199 & 6275
Rev limiter set on PCM is 6700 in 1st and 7k other gears, although Kur4o's XDF lists a setting of 6375(MAX RPM for 0 bpw)
I'd presumed the PCM was limited to 6375 RPM but did log 6795 on the way home.
I'd never got the motor over 6400 previously.

AFR was off wideband & connected to EEHack.

Just looked at another printout of a 5th Gen . RR150 & TN 3.721

I'll see how I do at the track Saturday.
It was definately struggling for breath with the map dropping down.
I guess that's more likely the intake rather than exhaust, so a throttlebody first is the easiest fix.

Headers are doable but i'd want to do duals and need cats and cutouts, so the cost has just escalated.


Thanks for the insight sir
Mitch

[terminal_crazy]

Little update
Ordered a 58mm Holley Throttlebody (I know you say 52 is enough but it costs bugger allmore so why not. )
Ordered Speed engineering's 1 3/4 long tube headers.
I guess the single 3" exhaust & single cat was a bigger restriction than the 1.5" mid length headers.
Plan is dual cutouts and keep the single pipe.


However, I did pull the intake to reseal the rear chinawall.
The AFR intake gaskets had delaminated and the head half of the gasket had pulled 7-10mm into each of the 4 outer ports.
I conclude the manifold obviously was NOT clamped down properly.
I couldn't see any evidence of any vacuum leaks.

I've remeasured the intake/head angles and are slightly wider than recommended at the top of the heads.
Gaskets did have clamp marks top & bottom.
I conclude the manifold might have been held up by the threads on the bolts, but couldn't see any evidence.
Bolts holes were clearanced some more & manifold refitted.

Car idles ok & drives ok but i've not bothered retuning yet until headers get swapped next month.
IAC counts have gone up 10-15 points which may or may not indicate a prevoius vacuum leak.


When headers are on I'll get it back to the dyno for an update.
Thanks for the help.
Mitch

[Injuneer]

Have the intake manifold throttle bores been opened up to 58mm?

If the manifold gaskets we’re spreading into the port flow area, that’s another obstruction to good breathing.