Scottie-GNZ Posted February 12, 2001 Share Posted February 12, 2001 When I ran my L28T, it winged its way to a trapspeed of 110.97mph with the little stock T3 turbo wheezing it lungs out . Between the 1/8 and 1/4-mile mark, it had an elapse time of 4.45 and gained 27.43mph! The GNZ has over 100hp more, ran the 1/4-mile 1.7 secs quicker and 11.54mph faster but only gained 24.87mph from the 1/8 to the 1/4. The weight of the car is almost identical and nothing has changed aerodynamically. The 2 engines have completely different HP curves, but with 100hp more, why is the GNZ at least not gaining 27mph in the 2nd half? ------------------ Scottie 71 240GN-Z Scottie's GNZ Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted February 12, 2001 Author Share Posted February 12, 2001 I have certainly given all of that a thought. I used to spin the L28T to 6250 and I spin the Buick to 53-5400. The L28T had a 3.70 LSD and 24.5" tires and the Buick has a 3.54 with 26" tires. The Buick gearing closely matches the factory and appears better suited for top-end power. If anything, the L28T gearing was not optimum for a T3 turbo except for the fact that I had the big I/C and willed more power out of it tuning the SDS. All of that said, the fact remains (and what is puzzling to me) I now have over 100hp and ungodly amount of torque to pull me through the top-end. Why is that not generating a bigger speed difference between the markers? For those who remember, read old-timers , they used to say the same thing about the Greenwood Corvette with its low-revving BBC and he would get up on the Daytona banking and just walk away from everyone clicking off 220+mph in the days before the dog-leg. No need for a debate, just pondering. Maybe when I get the injectors and run 24# boost I will get 27mph, but then I will have closer to 150HP more and then ask why not 30mph . ------------------ Scottie 71 240GN-Z Scottie's GNZ [This message has been edited by Scottie-GNZ (edited February 12, 2001).] Quote Link to comment Share on other sites More sharing options...
Drax240z Posted February 12, 2001 Share Posted February 12, 2001 I have a theory which comes to mind, but I haven't really thought it out. Hopefully I'll be able to make some sense of it by the end of the post. Lets say for instance with the L28 you were going 80mph after 1/8th, and gained 25mph in the 2nd 1/8th. Ending at 105mph.(just random numbers!) Ok, the GN with the extra power might be going 95mph in the 1/8, and gaining only 20mph int he 2nd 1/8th, ending at 115mph. The first thing that comes to my mind is aerodynamic drag. You can't really compare your gains in the 2nd 1/8th mile, because you are allready travelling faster with the GNZ than with the L28. I believe aerodynamic drag increases as a square to your speed increase. Double the speed, 4 times the aerodynamic drag! Thats my theory anyway. But I would think that the spoolup problems, injectors at 100%+ duty cycle, etc also are corrupting your data slightly. ------------------ Richard Lewis 1972 240z - L28TURBO transplant ongoing! Drax's 72 240Z Turbo Quote Link to comment Share on other sites More sharing options...
pparaska Posted February 12, 2001 Share Posted February 12, 2001 I'm thinking along the same lines as Drax. The total drag is proportional to what, the cube of the speed? That ~10 mph difference at the 8th between the two drive trains/tires might be all in that aero factor. I know Aero Drag = 1/2 (density)*Cd*Area*Vel^2 But doesn't road and drivetrain friction account for another power of Vel. proportional drag, making the effect of vehicle velocity on drag somewhat more like a cube power dependence? Inquiring minds want to know. Pete (I ain't no aerodynamicist) Paraska [This message has been edited by pparaska (edited February 12, 2001).] Quote Link to comment Share on other sites More sharing options...
johnc Posted February 12, 2001 Share Posted February 12, 2001 All in good fun... Scottie, I think it comes to your "third derivative of position" or jerk-factor: It is well known that the first derivative of position (symbol x) with respect to time is velocity (symbol v) and the second is acceleration (symbol a). It is a little less well known that the third derivative, i.e. the rate of change of acceleration, is technically known as jerk (symbol j). Jerk is a vector but may also be used loosely as a scalar quantity because there is not a separate term for the magnitude of jerk analogous to speed for magnitude of velocity. Many other terms have appeared in individual cases for the third derivative, including pulse, impulse, bounce, surge, shock and super acceleration. These are generally less appropriate than jerk, either because they are used in engineering to mean other things or because the common English use of the word does not fit the meaning so well. For example impulse is more commonly used in physics to mean a change of momentum imparted by a force of limited duration [belanger 1847] and surge is used by electricians to mean something like rate of change of current or voltage. The terms jerk and jolt are therefore preferred for rate of change of acceleration. Jerk appears to be the more common of the two. It is also recognised in international standards: In ISO 2041 (1990), Vibration and shock - Vocabulary, page 2: "1.5 jerk: A vector that specifies the time-derivative of acceleration." Note that the symbol j for jerk is not in the standard and is probably only one of many symbols used. In the aerospace industry they even have such a thing as a jerkmeter; an instrument for measuring jerk. So, Scottie, I think you need to hook up one-a-dem jerkmeters. Sorry list, I couldn't resist posting this 'cuz I found it yesterday when researching a physics thing. Gotta find me a jerk 'o meter somewhere (most people suggest that I peg the meter...) ------------------ John Coffey johnc@betamotorsports.com Quote Link to comment Share on other sites More sharing options...
pparaska Posted February 12, 2001 Share Posted February 12, 2001 John, you crack me up. Yeah, the "jerk" put out by the L28T was higher, that's why it "jerked" more in the last 18th mile. Yeah, that's it . Quote Link to comment Share on other sites More sharing options...
johnc Posted February 12, 2001 Share Posted February 12, 2001 Exactly! Scottie's Z has a lower jerk factor that the when he was running the L28T. I'm thinking he needs to increase his vehicular jerk factor. Maybe a big wing on the back? ------------------ John Coffey johnc@betamotorsports.com [This message has been edited by johnc (edited February 12, 2001).] Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted February 13, 2001 Share Posted February 13, 2001 quote: Originally posted by johnc: I think its your jerk-factor: In ISO 2041 (1990), Vibration and shock - Vocabulary, page 2: "1.5 jerk: A vector that specifies the time-derivative of acceleration." In the aerospace industry they even have such a thing as a jerkmeter; an instrument for measuring jerk. [/b] Okay, I thought the slide-rulers were off limits to John; or was that just sharp instruments in genreral? Quote Link to comment Share on other sites More sharing options...
John Scott Posted February 13, 2001 Share Posted February 13, 2001 What were/are your 1/8 MPHs? Surely the GN has a much higher 1/8 speed?? If you're starting from a higher speed then its going to take lots more power to get a 27 mph spread. JS Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted February 13, 2001 Author Share Posted February 13, 2001 John, put down the pipe and slowly back away No John, not side-to-side, backwards. As for the 1/8 and 1/4 mph, here they are and no, I am not jerking you guys around, that is not a typo. L28T - 83.54 & 110.97 GNZ - 97.64 & 122.51 ------------------ Scottie 71 240GN-Z Scottie's GNZ Quote Link to comment Share on other sites More sharing options...
Drax240z Posted February 13, 2001 Share Posted February 13, 2001 LMAO! Too funny. The dumb part is that I'm reading along and thinking "I don't remember ever hearing about this in engineering!" Haha. I still like the grassy knol... er, aerodynamic drag theory. ------------------ Richard Lewis 1972 240z - L28TURBO transplant ongoing! Drax's 72 240Z Turbo Quote Link to comment Share on other sites More sharing options...
johnc Posted February 13, 2001 Share Posted February 13, 2001 OK, so you guys wouldn't go for my jerk factor theory. I think drag is the correct answer. If someone with a more mathematical bent can solve this equation, I think we can find out how much power Scottie needs to generate to experience the same level of jerk... Power required to overcome drag: P=Fd*v=1/2Cdpv3A P = Power Fd = drag force (Fd=1/2Cdpv2A) v = Velocity Cd = Drag Coefficient (Cd=Fd/1/2pU2L2) p = Fluid Density A = Cross Sectional Area I'm not a mechanical engineer and just barely a software engineer, so math just confuses the hell out of me. ------------------ John Coffey johnc@betamotorsports.com Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted February 13, 2001 Share Posted February 13, 2001 Who are you and what have you done with scottie! It is, like you said, a different engine, with different gear ratios in the transmission, and different power curves..... ------------------ Morgan http://z31.com/~morgan/s30 http://carfiche.com Quote Link to comment Share on other sites More sharing options...
Mikelly Posted February 13, 2001 Share Posted February 13, 2001 Yup, sounds like your boost, torque curve and where the HP comes in at is way different on this platform than the L series platform you used to run. You need to get more balance across the rev range so your HP will be there to push you through the traps when the torque starts to fall off... Just my guess, but the fact that you mentioned your injecter being maxed out, that isn't helping your situation at all! Mike ------------------ http://hometown.aol.com/dat74z/myhomepage/auto.html "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
blueovalz Posted February 13, 2001 Share Posted February 13, 2001 I feel the main focus on this is the torque and rpm relationship. Read the following site www.vettenet.org/torquehp.html and you may find your answer. I will only take a few minutes and is well worth the read (then you can impress your significant other with more gearhead talk). Terry Quote Link to comment Share on other sites More sharing options...
Guest LoFlyingZ Posted February 13, 2001 Share Posted February 13, 2001 Thanks Terry! That was an awesome article. Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted February 13, 2001 Share Posted February 13, 2001 quote: I feel the main focus on this is the torque and rpm relationship. Terry [/b] Scottie, I feel Terry is correct. Look at the comparisons between your L28Tz & GNz. About the same weight. The fact you obtained a low 14Et from the miniscule torque output of the L28Tz is proportional. Keep in mind you had larger rear gears & smaller tire diameter for the L28Tz; this allowed you to run your RPM's higher-keep your speed up on shifts & stay on top of what power was being put forth. Now you have the same car w/different engine; or a different car w/different engine; anyway, you have higher gears (3.545) & larger tires. In your old set up your overall gear ratio (including tires/rear gears w/trans 1:1 ratio) put you at the 3.7/3.9 area. With your current set up you now have an overall gear ratio of 3.4; all that to say this-you have more hp but your rpm's are lower. I will confess I'm not up on the Buick V6 power curve nor turbo's/superchargers-but my #'s I ran; whose peramiters mock your set up indicate your putting out 290-314hp (RWHP). That's not to shabby from a V6-even if it is turbo'd. All in all I feel you've max'd out your current set up; unless you still have a few tricks up your sleeves I think the only alternative would be to run slightly smaller tires in an attempt to increase your rpm's at the trap. Until you break that wall (Sound Barrier) I think the drag factor has your number on it. And we all know what a "Jerk" the drag factor can be sometime-All right John, What did you do w/my Jerk-meter? Just my .02c worth. [This message has been edited by Kevin Shasteen (edited February 13, 2001).] Quote Link to comment Share on other sites More sharing options...
Drax240z Posted February 13, 2001 Share Posted February 13, 2001 Kevin, I think you are grossly underestimating the power of both engines here! Scotties 13.09@110.97mph with his L series puts him at 293rwhp, given a 2750lbs car. The 11.5@122mph with the GN puts him somewhere around 389rwhp, in a 2750lbs car. As Scottie can attest to (and I've learned from reading some buick sites out there) these engines can produce INSANE horsepower. I believe Scotties has hardly scratched the surface of what this setup can do, and I don't think he's anywhere close to maxing it out! Hell, Derek Grub runs 10.x? with the same engine! ------------------ Richard Lewis 1972 240z - L28TURBO transplant ongoing! Drax's 72 240Z Turbo Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted February 13, 2001 Share Posted February 13, 2001 quote: Originally posted by Drax240z: Kevin, I think you are grossly underestimating the power of both engines here! Scotties 13.09@110.97mph with his L series puts him at 293rwhp, given a 2750lbs car.The 11.5@122mph with the GN puts him somewhere around 389rwhp, in a 2750lbs car. Drax, Sorry bout the confusion-Scottie-I certainly wouldnt want to short anyone on their pride-n-joy. I was on an empty stomach when I first ran my set of #'s. Had to go thru all the forums before I found Scottie's previous post where he gave times w/his mph's. I admitted earlier I was in unfamiliar territory when it came to turbo's & superchargers: still we are talking about the bottom line-ET's & MPH at the end of the 1/4. After recrunching the #'s...this time two & three times to confirm the outcome: this is what I came up with. Scottie's previous postings of his most recent ET's/Mph: 1) 11.38 @ 118.26 2) 11.8 @ 121.86 3) 11.9 @ 122.51 There are multple ways of figuring hp; You can obtain HP from weight/Mph or you can obtain HP from ET's & Weight. I ran both. I only ran Scottie's first & last runs as they indicate his fastest ET & Fastes MPH. 1)From his best ET of 11.38 I took that number & Divided it by 5.825 & with that answer 3'd (Cubed) it; then took his 2800lbs (weight of his car w/him in it) & divided that by the previous answer......this equals 375hp. 2)From the third run I took his quickest MPH of 122.51 & divided that by 234; this number gets 3'd (Cubed); after cubing it then take that number & multiply it by 2800lbs (weight of the car w/driver in it).....this equals to 396Hp. The 396hp figure; factored w/his 26"tires & 3.545 gearing should equate to a 121.9mph The 375hp figure: factored w/the above equate to a 119mph...exactly what his #'s indicated. We can stretch this out one step further to determine the theoretical ET. This is done by Dividing the weight of his car w/driver in it 2800lbs by the 396Hp; cube root that number & multiply it by 5.825...this should yield an 11.1 ET. Yes I messed up somewhere in my first calculations. However, My point still stands...if the same old thing isnt getting you where you need to be; then you cant expect any improvements by doing the same old thing....something has to change. Its obvious his car is stronger in the first 1/8mile & not as strong in the 2nd 1/8 mile. There needs to be a balance. Torque will fall off when V.E.(Volumetric Efficiency) begins to fall off. This is unavoidable as rpm's get further away from maximum V.E. However, one who races needs the torque fall off to be somewhere in the proximity of where HP peaks; after all-HP is a function of torque, not the other way around. If you can balance out the torque/Hp-which the proper gearing will do: this should yield you a better balanced ET-both in the first 1/8th mile & in the last 1/8mile of the 1/4. Isnt this what we gearheads are always doing-attempting to obtain the most power & then trying to stay on top of the powerband w/in a limited distance traveled? Good luck Scottie in figuring it out & congrat's on hitting the 11's...the Low 11's; very few of us ever get to that mark. Again; just my .02c worth. [This message has been edited by Kevin Shasteen (edited February 13, 2001).] Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted February 14, 2001 Share Posted February 14, 2001 quote: Originally posted by Scottie-GNZ: The why is the GNZ at least not gaining 27mph in the 2nd half? [/b] Scottie, I hate unresolved issues. As I've said previously-I'm not familiar w/turbo's nor the Buick V6's powerband. However, I'm very familiar w/tire sizes, gear ratio's & the ole 1/4mile formulas. Here's my take on a possible even powerbandfor the 1/4mile. As we all know you posted three recent runs; each gave a best ET,MPH & 1/8 mile yet none were in the same run. What I did was took the best of all three; as this indicates what your car is capable of doing & played w/nothing more than the tire sizes. Your currently running: 1) 2800lbs car w/driver in it 2) Best of all three runs yielded a) 396HP 11.3 ET c) 122.51mph 3) 3.545 rear gears 4) 26"tires...(actually 25.8"tires) Now; doing nothing more than up'ing the tire diameter-we can notice the difference in mph; but first we have to determine your RPM's at you fastest 122.51 run. Correct me if I'm wrong but my figures indicate your RPM's are @ 5655 at the 1/4traps. I) Your already running 275/50/15 A) 275/50/15's yielded 5655rpm's @ 122.51mph 275/55/15's would put 5655rpm's @ 127.7mph C) 275/60/15's would put 5655rpm's @ 132mph These are theoretical #'s of course; but its something to think about. The larger tire size would lower your rpm's & help your engine stay on top of its Powerband; as you've indicated...it appears your car is stronger in the first 1/8mile than the last. At least that's my take on it; once you get the FI/Boost & all that other turbo stuff figured out-you might break the 10's. One last comment-Do you drive this car to the tracks or trailor it; if you drive it do you feel your exhuast may inhibit the eng's ability to breath hurting the turbo's ability to "Power Up"....probably a stupid quesiton coming from someone who doesnt understand turbo's. If this is a trailored car; why dont you lose the alternator & add a 2nd turbo-that should get you into the 10's relatively easy; of course "Relatively Easy" is a relative term. Ok...that makes my .02c worth now for about the 4th time; does that mean ya'll had to endure me for .08cents worth? [This message has been edited by Kevin Shasteen (edited February 13, 2001).] Quote Link to comment Share on other sites More sharing options...
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