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#21 | |
![]() Join Date: Feb 2014
Location: AZ
Posts: 860
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Thanks so much for taking the time!! |
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#22 | |
![]() Join Date: Feb 2014
Location: AZ
Posts: 860
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#23 |
Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,696
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I call this my "Stairway to LT-5 Heaven" dyno graph. It shows the progression of power and torque through stages of modification and tune. The bottom one demonstrates a ported top end with secondaries tied open. The throttle plates had been removed however but the shafts remained albeit w the least surface facing airflow. The calibration has an injector "turn-on" delay which is eliminated when the secondaries are deleted or at least it should be.
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[SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX |
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#24 | |
![]() ![]() Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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However, Marc increased my idle to about 850 to help with smoothing the idle, and that all but eliminated it. As far as the rattle itself goes, it sounds like marbles rolling around in the transmission. It is noticeable? Yes. But, is it annoying? Well, that is subjective, and except for a cammed LT5 it is very subtle with good injectors and 850 rpm idle, IMO. (Note: My NOS injectors succumbed to alcohol in an insidious manner over a couple years. After replacing them, one of the unexpected bonuses was the near disappearance of the trans rattle.)
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Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry |
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#25 | |
![]() Join Date: Jul 2010
Location: Woodstock, Ontario, Canada
Posts: 1,275
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![]() From one of my previous posts, much more than 1/2 a point at the power torque peaks. Make sure you are NOT comparing teh numbers noted on teh actual graph, as they are giving power/torque numbers at 3900rpm which is NOT a peak for any of the curves. For peak outputs compare teh actual numbers at the top of the graph labelled MAX POWER/MAX TORQUE. "You can see the torque advantage of 30 lb/ft at 2600rpm for the closed Port throttles, but at just 4500rpm, the Closed Port Throttles give up roughly 45hp at 4500rpm to the open Port Throttles. At this same 4500rpm, the CLosed Port Throttles are all done and power falls off abruptly after than as airflow is choked off It should be noted that the low rpm torque difference between the Open vs. Closed Port throttles would increase if the dyno run was started at a lower rpm. It appears to be a significant low rpm difference between Open and Closed Port Throttles. The Open Port throttles continue to build another roughly 125hp from 4500rpm to their peak of 469hp at 6600rpm or so. All totalled the Open Port Throttles are worth an extra 160hp vs the Closed Port Throttles.(469 vs 309hp) and an extra 428 lb/ft of torque (417 lb/ft vs 389 lb/ft) when the entire vastness of the LT5 rpm range is considered." To keep or remove the Port Throttles, THAT is the question. And the true answer for you personally is exactly at what rpm you drive.launch/cruise. Get under 2000rpm and the torque difference gets larger, at least on the graphs. Basic answer to one of your questions, no, you cant retain your "power key" function once you delete your Port Throttles.
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peace Paul ZR-1 Net Registry Member #1494 Last edited by Hog; 06-07-2014 at 04:30 PM. |
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#26 |
![]() ![]() Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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The graph below is veering OT, but with regard to PORTING in conjunction with removing the SPTs, one of the myths so often bantered is how opening up the runners will slow velocity and thus "kill" low rpm torque. Bullshiet!
Apparently, the LT5s (especially the 90-92s) were starving for air (something addressed, perhaps, with the Gen II LT5 that was destined for the 95 ZR-1). ![]() ![]() This graph depicts the torque plotted for my stock LT5, and after being fully ported. The motor retains the stock cams AND throttle body (see my signature for more details). ![]() For planning purposes, removing the SPTs in conjunction with porting appears to buy back the 25+ pounds of torque advantage through 4000 rpm when in NORMAL power mode. And, of course, above 4000 rpm torque comparisons for the ported LT5 simply runs away from the stock performance. What a shame Graham's new GEN II LT5 baby never saw the light of day. To use a phrase borrowed from Mike 100, there's a lot of "low hanging fruit" available with the LT5 - and 500+ hp is possible w/o compromising the nikasil liners or stock cams; i.e., the reliability.
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Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry Last edited by Paul Workman; 06-08-2014 at 10:28 AM. |
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#27 |
![]() Join Date: Jul 2010
Location: Woodstock, Ontario, Canada
Posts: 1,275
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Was the OBD2 LT5 engineered for roller cam followers, I cant remember?
EDIT-The mods I was referring to were part of the planned 1995MY upgrades to 475 bhp, that ended up being as tillborn project, unfortunately. It was incorrect for me to refer to the 1995MY upgrade engine as the "OBD2" engine although the upgraded engine would have required OBD2 qualification for MY1996.
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peace Paul ZR-1 Net Registry Member #1494 Last edited by Hog; 08-07-2014 at 03:24 PM. Reason: Correction |
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#28 | |
![]() Join Date: Dec 2003
Location: Arcadia,OK
Posts: 3,384
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The gear rattle is of no consequence to me because I am seldom ever in the car with the clutch engaged, in neutral. Some folks do that at stop lights, I don't. The lighter flywheel takes a little street driving adjustment because of the lighter rotating mass & faster spin-up. Likewise, if you are drag racing, the correct launch rpm & clutch release is more critical, walking a fine line between bog & excessive wheel spin. Doug Rippie used to offer a 24# iron LT1 flywheel for the LT5 that was popular. It helped mitigate the street driving & drag racing issues while shedding several pounds from the D/M flywheel. I would expect the heavier flywheels would also help reduce the transmission rattle. Fidanza 13# (alum billet) Jerrys Gaskets 18# (alum billet) Jerrys Gaskets 22# (alum billet) Stock D/M 33# McLeod (I don't know the weight, guessing around 16~18#)
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Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 ZR-1, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed. |
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#29 |
![]() Join Date: Dec 2003
Location: Arcadia,OK
Posts: 3,384
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I don't know if the OBD2 is the same as the 95 MY 475Hp LT5 that never made it to production, or not. If it is, the answer is no.
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Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 ZR-1, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed. |
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#30 | |
![]() Join Date: Apr 2007
Location: Lake Bluff, IL
Posts: 2,063
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I also had the secondaries removed when Marc did his work and I notice no issues without them. The car runs strong and although Marc and others say you do lose a little low end torque, I certainly don't notice it.--Bob
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2016 Long Beach Red Z06 #10281 "POPS Z" 1995 Polo Green #409 "WARP TEN"--Haibeck 350/510 package, 4.10s, Hurst, Stock Exhaust with QTP Cutouts --Sold but still running strong 1993 Quasar Blue #161 "HIL KING" --Sold but still running strong, now with more than 120,000 miles 1967 Marlboro Maroon/Saddle Corvette Coupe 300 hp/4-spd --Sold a long time ago ZR-1 Net Registry Founding Member #95 NCM Lifetime Member Favorite Quote--Attributed to Mickey Thompson: "Too Much Horsepower is Almost Enough" Last edited by WARP TEN; 06-09-2014 at 11:04 AM. |
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