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  1. #1
    LTX Member


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    Mitch
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    '95 Z28 LT1 M6
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    Default 1st dyno session - A little disappointed

    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

  2. #2
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    Fred
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    1994 Formula - SOLD
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    Default

    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?
    SOLD - GONE TO A (VERY) GOOD HOME ! - 94 Formula A3+1: 381ci forged stroker - Callies Stealth, Oliver 5.85 billet rods, BME nitrous pistons / CNC LT4 heads / CC solid roller / TH400+GearVendors OD / 4.11 Strange 12-bolt / 300-shot N2O / Spohn Suspension / roll bar / MoTeC M48 Pro engine management system /a few other odds 'n ends.

  3. #3
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    Default

    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

  4. #4
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    '95 Z28 LT1 M6
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    Default

    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



    IMG_0824-Dyno_Sheet_Inverted.JPGIMG_0824-Dyno_Sheet_Inverted.JPG


    Thanks
    Mitch

  5. #5
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    Default

    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

  6. #6
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    Default

    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.
    Last edited by Injuneer; 07-26-2019 at 09:59 AM.
    SOLD - GONE TO A (VERY) GOOD HOME ! - 94 Formula A3+1: 381ci forged stroker - Callies Stealth, Oliver 5.85 billet rods, BME nitrous pistons / CNC LT4 heads / CC solid roller / TH400+GearVendors OD / 4.11 Strange 12-bolt / 300-shot N2O / Spohn Suspension / roll bar / MoTeC M48 Pro engine management system /a few other odds 'n ends.

  7. #7
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    Default

    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.

  8. #8
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    Default

    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

  9. #9
    LTX Member


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    Default

    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

  10. #10
    Long Live the Opti


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    Default

    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.
    Quote Originally Posted by Ryan Stout View Post
    I would try to work my neck muscles but I'm not invited to the LS guy parties.

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