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#11 | |
![]() Join Date: Sep 2010
Location: Currituck, NC
Posts: 246
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#12 | |
![]() Join Date: Nov 2006
Location: dayton,ohio
Posts: 425
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[FONT=Comic Sans MS][COLOR=red]"I wanna go fast!!"[/COLOR][/FONT] [FONT=Comic Sans MS][COLOR=#ff0000]-- Ricky Bobby[/COLOR][/FONT] |
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#13 |
![]() Join Date: May 2005
Location: Nichols, FL
Posts: 615
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I might as well interject a thought. While cavation could be a problem and is a known issue with the LT-5 I would contend that the bypass system is the root of the problem and much easier to solve.Mark is correct that the engine heat generated by rpms over 6100 rises faster than one in a racing environment can contend with, however this is due more to the fact the water ceases to flow through the radiator when the rpms pass 5800 or so rpms. In fact over 5800rpm the water is routed directly back into the block via the bypass which helps explain the dramitic increase in temp.
I do not have the skills to reengineer the bypass but I have tested in normal driving and at least one owner tested in racing the following. 1. Install a radiator that can flow at least 100 gpm. 2. Cut the thermo spring so that it is always open. 3. Block the bypass flow path with a plug. I ran this configuration for over 50k miles with no overheating, in fact I had to block the radiator with cardboard in winter to have enough heat for the heater. This configuration was what Fastlane used in his car (it was he who told me this trick) and was tested by at least one roadracer with satisfactory results. Tyler
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55 Polo White (Project) 61 Jewel Blue (Sold to buy above) 66 Nassau Blue 68 Torch Red 88 ZR1 Blue 90 ZR1 White |
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#14 |
![]() Join Date: Sep 2010
Location: Currituck, NC
Posts: 246
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I'm all ears! I'll explore all options!!
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#15 | |
Join Date: Aug 2008
Location: Houston 90 Red ZR-1
Posts: 2,320
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#16 |
![]() Join Date: Sep 2011
Location: TN
Posts: 581
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Ok as far as heat - would it not help if the water pump was ported in some way ( to create more flow)? what about using waterwetter ? Are there any part numbers for a higher flow radiator?
I too used to cut the spring (center) out of my thermostats and just use it as a restrictor to help slow the water down a little... it always helped.. |
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#17 | |
![]() Join Date: Jul 2005
Location: Cresson, TX
Posts: 970
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This is from Marc's website: Upgrade: '90-'92 Original equipment engine power 375 Low back pressure exhaust system +10 Performance engine calibration (chip) +10 Subtotal 395 Long Tube Headers +25 Subtotal 420 420x.85=357 So not too far off... Cheers, RH |
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#18 |
![]() ![]() Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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Shrek,
Asside from a (low?) 309 hp baseline, 30 hp gain seems about right compared to the results others have had for the same mods, as well as what Marc H's web site data suggests. That's a good thing, but it tends to support (in my mind anyway) that the baseline number may be even more indicative of something else that "ain't quaht raht" here. For example, here is a bone stock 90 (except for a Borla cat-back exhaust) that pulled 339 rwhp - pretty close to what yours makes after headers, etc. THIS is what makes me wonder if there is a gremlin that needs to be rooted out in the base case, as your car responded very much in line with what others experience for the same mods. Note: On the dyno runs (below) the A/F ratio was getting too lean - turned out the secondary fuel pump was not working - so the operator was cutting it off at around 6k rpm. And, note it was stock except for a Borla cat-back. (The resonator tubes diameter were something like 1-3/4": no resonance, but also "a bit" restrictive too.) ![]() Shrek, I hope you don't think I'm being a "Debby Downer" or throwing cold water on your improvements. It is because the improvement value is typical that it brings attention to the fact the baseline and end results are not what is also typical, and there may be a reason - maybe even a simple fix - for it. For example, Dom discovered the secondary throttle plates in his TB weren't opening fully when the accellerator was floored. A simple adjustment and voila! Same thing happened on my wife's C3. I'm just sayin, 20+ hp is 20+ hp. And, hell...guys spend $300-$400 to pick up 5 hp from porting the TB! So, I'll shut up about it now, but I just thought it might be worth a look. Could be dyno error too, for that matter. Good luck! P. PS: I just noticed something... The new torque number is higher than my baseline number, but the hp is not. Is the torque/power curve dropping off suddenly above 6000 rpm or was the run cut off prematurely? Any chance we could see the dyno sheets - before and after??? That might be the answer to this question. If it is, then we'll know.
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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; 02-13-2012 at 07:54 AM. |
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#19 |
![]() Join Date: Sep 2010
Location: Currituck, NC
Posts: 246
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Not a problem Paul. There could have easily been a problem with the motor way back then. My guess would be injectors! I was always a little bummed about the 309, because the other two 91's that day pulled high teens and low 20's. But the car always ran smooth and felt like good power for a weekend cruiser for the wife. That was until the injectors caused it to start bucking and missing last year. I put in a set of FIC injectors and could tell right away that we had more power than before but never got it to the dyno to confirm my butt dyno. My guess is we could probably get more power now with a custom tune. It was definitely running a tad rich on this tune from Marc, but since she probably wouldn't notice the difference, I'm going to play it safe and let her have at it like it is.
I'll get a copy of each dyno posted up. ![]() ***EDIT*** Here are the sheets! 2003 ![]() 2012 ![]() Last edited by Shrek; 02-14-2012 at 07:33 AM. |
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#20 |
![]() Join Date: Sep 2010
Location: Currituck, NC
Posts: 246
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She's going to run with the NASA group first, then we'll branch out to some other clubs. Even though she has many, many laps on track with the NCCC, we're going to start her off in group one until she learns to play nice with other cars on the track.
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