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Why the LT5 was discontinued...

 
Old 04-24-2019, 10:36 AM
  #21  
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Originally Posted by Dominic Sorresso View Post
Marty,

Very interesting. If true, it clearly demonstrated the NIH mentality pervasive at Powertrain.
Think about this. There were some at GM willing to tell the nearly 7000 owners of the C4 ZR-1 that GM had just shafted them for an additional $30k on a motor that was not any better than a warmed over SBC.
Great customer loyalty.
I think who ever set this “test” up certainly didn’t want to try it up against the 3rd Gen LT-5 Lotus was proposing given that the cam phasing for that motor would have eliminated any “low end torque” advantage an LT4 would have.
I say all this and still must recall that at the time, the Vette was on the corporate ropes. So did some people do what they thought they needed to do to save the car from the green eye shade people? No doubt, as documented by McLellan and others that their love for the Vette is unquestionable. Maybe Barra is one if thise people along w Reuss.
Dom,
Well said!
Imagine that.
You mean General Motors had their own "deep state" or swamp.
I am so shocked!
First thing you learn in business, is don't mess with another's rice bowl.
Perhaps that "Lotus Business" peed a few folks off?
Revenge was sweet.
Marty
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Old 04-24-2019, 10:39 AM
  #22  
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Originally Posted by Tom400CFI View Post
OK, got it. So that was all "made up". Thanks for the honest clarification.

FYI, The 700R4 has worked just fine, behind more than a few engines that "enjoy high revs". Not that that matters when we're talking about low end tq and throttle response in this "blind test".
A bit more honest than many of your "statements of FACT"?

Just read any of your posts in this piece,

Made up?
Yes, YOU would say that from your vast ZR-1 and FSM experience!

If you can't see "RIGGED" get your eyes checked.

Marty
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Old 04-24-2019, 10:54 AM
  #23  
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Originally Posted by DRM500RUBYZR-1 View Post
A bit more honest than many of your "statements of FACT"?
Right. Is that like, "your opinion is fact"? Show me where I made something up would you? I'd appreciate that, so that I can fix it. Thanks, buddy. Nice attempt at a pot-shot on the FSM too.

I get it though. People often move to insults etc. when they're called out. I'm used to seeing that.




I think I MAY have found where I read the "blind test" story originally -although I'm still not sure, b/cthe published date on that is 2017. I'm pretty sure that I read the "blind test" story further back, than that. I still can't believe that it's not in CFTI or HOTB. I was so sure that it was in there. Anyway, SuperChevy did a piece and talked about it, HERE about 7 "paragraphs" down.

Says about the same thing as the LSengineDIY site said. Having driven several ZR-1's and penty of seat time in LTx car....I don't see how the blind test could have convinced management that the LT engine had better throttle response. HP graphs from the era show that the LT5 makes more low end tq, I believe.


.

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Old 04-24-2019, 11:32 AM
  #24  
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Originally Posted by Tom400CFI View Post
Right. Is that like, "your opinion is fact"? Show me where I made something up would you? I'd appreciate that, so that I can fix it. Thanks, buddy. Nice attempt at a pot-shot on the FSM too.

I get it though. People often move to insults etc. when they're called out. I'm used to seeing that.




I think I MAY have found where I read the "blind test" story originally -although I'm still not sure, b/cthe published date on that is 2017. I'm pretty sure that I read the "blind test" story further back, than that. I still can't believe that it's not in CFTI or HOTB. I was so sure that it was in there. Anyway, SuperChevy did a piece and talked about it, HERE about 7 "paragraphs" down.

Says about the same thing as the LSengineDIY site said. Having driven several ZR-1's and penty of seat time in LTx car....I don't see how the blind test could have convinced management that the LT engine had better throttle response. HP graphs from the era show that the LT5 makes more low end tq, I believe.


.
Tom, News flash for you.
YOUR opinions are not facts either.
Just making certain that you understand that.

I am not surprised that you "don't see it"
My opinion on driving both LT-4 and LT- 5 cars reveals the LT-4 car to be more "responsive" in around town driving without coaxing.
Throttle response to input is far more linear in the LT-4 car.
Was it a trick of accelerator design? I don't know, but the test would be close in everyday driving even with 2 manual transmissions.
At least until full power is summoned.
And yes Tom, to be clear that is opinion.
Very experienced opinion from years of ownership and many miles of driving both cars.
That very experience is what reinforces the convincing nature that the test you cited was rigged to favor the LT-4 car, for some reason.
Drive both cars extensively and you will likely formulate the very same opinion.
Marty
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Old 04-24-2019, 12:43 PM
  #25  
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Originally Posted by Tom400CFI View Post
HP graphs from the era show that the LT5 makes more low end tq, I believe.
I thought so...

This GM produced graph shows the LT5 as making just a hair under 300 lbs at 1000 RPM.






And this graph shows the LT4 as making ~285 lbs





My experience driving ZR-1's and LTx's is that they have similar/same throttle response. There has to be more to the "Blind test" story that that LS leg humping article shared. I don't see how the exec's could have picked one over the other from an SOTP experience. Auto or stick. I hope ^that^ objective data doesn't offend anyone.
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Old 04-24-2019, 01:01 PM
  #26  
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Originally Posted by DRM500RUBYZR-1 View Post
Tom, News flash for you.
YOUR opinions are not facts either.
Just making certain that you understand that.
I totally understand that. Where did I state otherwise? If I did that, could you please quote where I did that...so that I can correct it? Thanks buddy!


Originally Posted by DRM500RUBYZR-1 View Post
My opinion on driving both LT-4 and LT- 5 cars reveals the LT-4 car to be more "responsive" in around town driving without coaxing.
Throttle response to input is far more linear in the LT-4 car.
Was it a trick of accelerator design? I don't know, but the test would be close in everyday driving even with 2 manual transmissions.
At least until full power is summoned.
And yes Tom, to be clear that is opinion.
Very experienced opinion from years of ownership and many miles of driving both cars.
That very experience is what reinforces the convincing nature that the test you cited was rigged to favor the LT-4 car, for some reason.
Drive both cars extensively and you will likely formulate the very same opinion.
Copy that. That was actually a useful and well presented post. Thank you for that and for keeping the 'tude out of it.

I've driven both and have not made the same observations that you have...however, I've not driven both extensively, so I'll take your word for it. Was it throttle linkage related? I'd bet it was but IDK. I'd BET that the two blade TB on the LTx lets in more air, per degree of throttle angle compared to the tiny primary throttle blade on the LT5....but I hadn't noticed the functional diff in the drives that I've had the privilege of having.


.

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Old 04-24-2019, 01:10 PM
  #27  
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So your objective data is based on two torque numbers.
There's why you don't see it.

Drive the two cars Tom!
and don't be offended.

Marty
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Old 04-24-2019, 01:17 PM
  #28  
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Tom,
I love ZR-1's.
But...………...
In everyday driving, as said, that darn LT-4 car will make you fall in love too.
If it were 1996, and a leftover 95 ZR-1 was sitting next to a 96 Grand Sport convertible, then I would have picked the ZR-1.
Now...………………
If it was a daily driver...…………….
Tough choice!
Yes, it's that good! (except as previously noted)
Marty
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Old 04-25-2019, 05:31 AM
  #29  
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Originally Posted by DRM500RUBYZR-1 View Post
Tom,
I love ZR-1's.
But...………...
In everyday driving, as said, that darn LT-4 car will make you fall in love too.
If it were 1996, and a leftover 95 ZR-1 was sitting next to a 96 Grand Sport convertible, then I would have picked the ZR-1.
Now...………………
If it was a daily driver...…………….
Tough choice!
Yes, it's that good! (except as previously noted)
Marty
trap speed at the digs is a pretty good indication of rwhp. the lt4 cars are competitive with the z with the ZR-1 starting to walk the lt4 as the speed grows

out of the hole and qtr mile they turn pretty similar times as the lt4 is a bit under rated

as you see from the dyno charts, these v8s aren't too far apart lt5, ls6, lt4 pretty evenly matched

we see many lt4 cars dyno at over 300 at the tire so the 330 rating is lower on the rev range.
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Old 04-25-2019, 05:40 AM
  #30  
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Originally Posted by DRM500RUBYZR-1 View Post
This test was over before it began. The methodology used assured the LT-4 car would outshine the LT-5. The actual drives simply confirmed what the test developer knew form the outset.
Hooking up a stock LT-5 to an automatic prevents the motor from performing at it's best.
BB62 is spot on.
That test was about as rigged as the Car and Driver "GTO vs Ferrari GTO" test of 1964.
The winner of the LT/4/5 test was the gent who defined how it was to be conducted.

That said, and also acknowledging my love of the ZR-1, I have always said a C-4 LT-4 car is simply one of the finest "around - town " drivers of it's day. That engine / trans combo, just always seems to be in the sweet spot and is fun to drive.
That is until max POWER is summoned. At that point, your longing for the LT-5 will become clear.

I once beat a 426 hemi with a worked 389 Pontiac...………….. after I made him spend 45 minutes driving to 5 places to race.
By the time we ran, his car was so loaded up it was over before it began.

If you cheat well, you will likely win.
The designer of the test knew that very well.
Marty
the conversion to automatic doesn't kill the dragstip performance at all and it fact the car will 60 ft and perform much better as anyone who runs a car competitively will tell you

the 2004r with modern guts will hold upwards of 1000 hp and 800 ft lbs of torq

for example, let's look at the lpe turbo cars, nitrous cars, and a few high end lt5s that run automatics.

the tt lpe cars went deep into the 9s with an automatic. Prior to that conversion they were very difficult to 60 ft and wouldn't et in the 9s

I had similar experience with my TT z06 running 800 at the tire. with the 6 speed, best I could on drag radials what 10.5s at 144 with a 1.72 60 ft time (3.90 gears, wrong setup)

with an RPM racing automatic 4l65e, the car pulled 1.54 60 ft time and ets fell to 9.84 at 142

so I would disagree that you can't run an auto behind the lt5 just bring your wallet, it's expensive!!
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Old 04-25-2019, 09:30 AM
  #31  
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Originally Posted by Tom400CFI View Post
Dom....what are you talking about here? The LT4 doesn't have a "low end tq advantage", that I am aware of.
Tom,

I used “ “ as a way of expressing tongue in cheek.

As for trap speeds, my stock 92 ZR did 112s in the 1/4 on street tires. I don’t recall any LT anything being close to that stock.
Maybe ETs could be close, but not trap speeds. Any longer race, ie 1/2mile and adios.
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Old 04-25-2019, 09:48 AM
  #32  
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Originally Posted by Tom400CFI View Post
OK, got it. So that was all "made up". Thanks for the honest clarification.

FYI, The 700R4 has worked just fine, behind more than a few engines that "enjoy high revs". Not that that matters when we're talking about low end tq and throttle response in this "blind test".
Interesting read but I have no dog in this fight.

But power glides have been used behind high rev engines as well. lol
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Old 04-25-2019, 10:23 AM
  #33  
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Originally Posted by Dominic Sorresso View Post
Tom,

I used “ “ as a way of expressing tongue in cheek.

As for trap speeds, my stock 92 ZR did 112s in the 1/4 on street tires. I don’t recall any LT anything being close to that stock.
Maybe ETs could be close, but not trap speeds. Any longer race, ie 1/2mile and adios.
Huh. I somehow missed the " " in your post about the LT4 tq. In fact, I went back and looked and still don't see it. My bad.

Who was talking about Trap speeds?
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Old 04-25-2019, 12:14 PM
  #34  
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An automatic transmission, Powerglide, 3 or 4 speed, on any of these engines would be fine for a drag racing application.
The automatic could also possibly improve E.T's I would suspect.

However, an automatic hooked up to an LT-5, such as used in the test would be challenged trying to improve "feel" and responsiveness in daily driving situations.
Perhaps the newer 8 speed computer controlled transmission found in the C-7's would have the gear spread and the programmability to exploit the LT-5's strengths, again in common situations of traffic, speed, and use in everyday driving.

All three engines spoken about are, as almost all have stated, very similar in torque and horsepower.
It still seems difficult to imagine a four speed automatic of that day, having the ability to deliver responsiveness with an LT-5 engine that is happiest at 4-7,000 RPM.
I would not want to pull into the drive in at the bank or move in heavy traffic that is pulsating with such a combination.

The LT-4 was a magnificent improvement over the LT-1 with the extra horsepower and torque enabling it to, even today, be compared to the LT-5, which says a lot.

The newer LS motors?
Obviously they are also able to be compared with the LT-5, especially the later versions, which are even far more powerful than the LT-5 ( automatic or manual ).

Marty
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Old 04-25-2019, 01:11 PM
  #35  
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Originally Posted by DRM500RUBYZR-1 View Post
However, an automatic hooked up to an LT-5, such as used in the test would be challenged trying to improve "feel" and responsiveness in daily driving situations.

All three engines spoken about are, as almost all have stated, very similar in torque and horsepower.
It still seems difficult to imagine a four speed automatic of that day, having the ability to deliver responsiveness with an LT-5 engine that is happiest at 4-7,000 RPM.
I would not want to pull into the drive in at the bank or move in heavy traffic that is pulsating with such a combination.
I agree that an auto would "dumb down" the feel of an LT5...but it does the same to any engine. It's the fluid couple that does that (the tq converter). Once the LT5 got up to 4-7000 RPM, the automatic would actually feel relatively more responsive, since the effect of the converter is diminished, and likely even, locked up.

THere shouldn't be any "pulsating" with a converter/automatic transmission, unless you have a poorly running engine.

But I'm with you; I wouldn't want an auto for an LT5. Or an LT4. Or an LT1. Or....which is why I don't have any.
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Old 04-25-2019, 01:15 PM
  #36  
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Originally Posted by Rkreigh View Post
the conversion to automatic doesn't kill the dragstip performance at all and it fact the car will 60 ft and perform much better as anyone who runs a car competitively will tell you

!
Originally Posted by DRM500RUBYZR-1 View Post
An automatic transmission, Powerglide, 3 or 4 speed, on any of these engines would be fine for a drag racing application.
The automatic could also possibly improve E.T's I would suspect.

However, an automatic hooked up to an LT-5, such as used in the test would be challenged trying to improve "feel" and responsiveness in daily driving situations.
Perhaps the newer 8 speed computer controlled transmission found in the C-7's would have the gear spread and the programmability to exploit the LT-5's strengths, again in common situations of traffic, speed, and use in everyday driving.

Marty
Just a comment on these executive driving tests. There would be very little WOT evaluation. 0-20 mph at half throttle is considered a more important real world measure. "Tip-in" meaning the transition feel from when the accelerator is pressed to when the sensation of acceleration begins - and the quality of that acceleration is probably the key measure when evaluating one powertrain combination to another. The actual torque and HP numbers mean very little in these type of tests. A lot of attention is paid to the transmission feel when shifting from one gear to the next and the overall powertrain smoothness at various vehicle speeds and throttle openings. These type of tests are run for a variety of throttle efforts, and yes, there is some WOT feel testing, but that is usually not the make or break element of the tests.
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Old 04-25-2019, 01:20 PM
  #37  
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So like I think Marty was saying, the throttle's "cam ratio", or what ever you want to call the pedal travel to opening ratio, -that would have a large influence on the opinions of two similar motors that have different throttle ratios.
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Old 04-25-2019, 01:40 PM
  #38  
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Originally Posted by Tom400CFI View Post
So like I think Marty was saying, the throttle's "cam ratio", or what ever you want to call the pedal travel to opening ratio, -that would have a large influence on the opinions of two similar motors that have different throttle ratios.
For what it is worth, I was agreeing with Marty and just noting for Ron that these executive drive tests are not about drag racing potential.
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Old 04-25-2019, 01:57 PM
  #39  
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I don't think anyone was talking about drag racing, w/regard to the "blind test". I certainly know that I wasn't.
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Old 04-25-2019, 02:12 PM
  #40  
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Originally Posted by Tom400CFI View Post
I don't think anyone was talking about drag racing, w/regard to the "blind test". I certainly know that I wasn't.
I know you did not, but read Ron's post (#30). It is all about maximum performance which to me gets away from the topic of drivability and how these executive tests are run and evaluated. (And there is nothing wrong with Ron's post, but it does bring in a different element to the discussion.)
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