aboatguy

Looks like the LT1 has more low end torque than the L98. From 2300ish to 3300ish L98 has a torque spike vs the LT1 flatter torque production. Funny thing is my datamaster dyno runs always have the same shaped torque curve with the little dip and then the resumption of the climb...

Tom400CFI

This isn't right.
*First, peak tq on the L98 is at 3200, not 2500. At 2500, peak tq is no better than most any other 350 CID motor, including the LT1.
*Second, the "magic" in the L98 is absolutely NOT in a broad tq curve, b/c it doesn't have a broad tq curve...and the intake (the very thing that makes it the "magical L98" is what condemns it to a narrow tq curve! The tuned runner length is precisely what gives the L98 a peaky tq curve and....
*Lastly, why it has that "bad assed" feeling that people like so much.


Bingo. Anyone ever drive a VAG 1.8t? Audi A4/etc? They FEEL FAST! Why? B/c they ain't got SQUAT below 2500 RPM, and they ain't got nuthin' over 4k either. So you get this little "shot" of squirt from ~2500-4k and reletive to what comes before and what comes after...it feelsGREAT! But what is it in reality? A slow 150-180hp turd w/no low end tq and no high end tq either. Just one little shot in the middle....just like TPI w/it's resonance tuned intake. Tuned for 3200 RPM, and that's where it's all at for that motor.

Testiculese

L-98 had a 305 intake and very restrictive heads. With a proper 350 intake http://www.firstfuelinjection.com/ they exceed the LT numbers.

Testiculese

1 thing everyone forgets..the TPI intake as restrictive as it is, was based on wave tuning principals and could achieve decent VE %s---IE torque thats why the 84 numbers for torque are soooo close to the 96 numbers, and why the 91 has a higher peak torque number than any LT.
A tpi (when I say that I mean long runner) setup designed for a 350 cid engine based on wave tuning would destroy a short runner and they are available.

but all that means nothing the most important thing /issue is addressed below.

The main ...most important ..most crucial thing you ALL are forgetting is this...
the sexiness factor...when you pop the hood on an L98 you see this space-aged looking spider legged badazz freaking intake that just looks tough especially when chromed, google the pics...long runners, put fat runners on a TPI and they are even sexier...girls love long runners, but like big fat long runners even more. Pop the hood on an C4 LT what do you see? A metal breadbox with short 3 in runners tucked away underneath.
Oh I believe the L98s have bigger vaccume ***** as well. Girls like that too.

JohnC485

Well, this is interesting because of the dyno...but It's weird, at part throttles my l98 felt much stronger, at lower than my lt1 trans am.

cv67

Niiiiice



Flat powerbands are boring.

GREGGPENN

Could be the most relevant post on this forum....ever!



And, really, it works perfectly with the pictures posted above!

Tom400CFI

1. Say....WHAT??
2. Proven wrong, over and over again. Nice try though.

2.5. Pssst! Peak tq numbers for the L98 were equal to peak tq numbers for the LT1.

AGAIN: All the tuned runners do is "compress" the tq curve into a smaller RPM band and accentuate it in that narrow area....JUST like a tuned pipe does on a a 2 stroke.

vetteLT193

The butt meter and track meter proves the L98 is a solid engine down low. I loved the feel of my '87 when I had it... stop light to stop light a better car than my later LT1 powered Vettes.

We used to go to the track with one dude with a '90 coupe that would destroy us all in the 1/8 mile (including a '90 ZR1, '98 convertible, trans ams, vettes, etc.). We'd blow by him right at the end of the 1/4 at a much higher speed but not much better time.

Bottom line is the L98 is considered a "torque monster" because it is a fun freaking car to drive around. IMO, more fun on public roads than the LT1.

Now the LT4 though: That is L98+LT1 ++ more. I like the LT4 more than the LS1. The later C5 Z06 and C6 engines finally truly beat the LT4. That is the ultimate in torque (high and flat torque curve) and revving (great power on top!).

The extra 100 HP comes from all the things already mentioned. The real magic is the area under the curve on the torque side. It's about as flat as it gets and up there. If I remember right GM engineers were unleashed to do what they pleased to make the LT4... they spent about 100 grand doing it and in doing so surpassed the LS1 numbers. They underrated the LT4 so they wouldn't look ridiculous spending millions in development on the LS1. Anyone who has owned a few C4's and one of them is/was an LT4 will tell you how great that engine is.

Testiculese

Maybe when you compare the 84 to the 96...but lets compare the best of both:
According to Mike Antonick's (author of the corvette black book) in his book "Cor-vette specs"
1991 RPO L-98
MPFI
Compression 10:1
HP 245@4000
TQ 345@3200
*** those numbers are with the auto trans get the manual and you get to claim 250 hp and 350 Ft-lbs

1996 RPO LT4
SFI
Compression 10.8:1
HP 330@5800
TQ 340@4500

Thats why the L-98 feels like it pulls stronger, you can get to 3200 rpm much faster than 4500. This does 2 evident things:
1) Makes the l-98 seem like the power is right there ..immediately, that the engine doesn't have to spin up to 4500 to develop the TQ. Basically gives you immediate throttle response to alot of TQ.
2) The second thing is it makes the L-98 (because it makes so much torque at such a low rpm), engine seem like its not working as hard (or loud) as the LT engines for the same torque.

Remember HP sells cars, Torque moves them. Stoplight to stoplight the L-98 does smoke the C4 LT. Thats why people who had L-98s and bought LTs asked that question "where did my torque go?" even though the torque numbers were similar that normal driving rpms around town the LT just seemed ....lacking. Who wants to spin their engine up to 5k when doing just normal driving.

Kubs

Yeah I was going by memory on the numbers. However, look at the graph shown above. The L98 torque is pretty flat, where the LT1 torque actually dips DOWN in the middle. The L98 is at least always increasing. It is not much of a peak. A PEAK can only be felt at that point but the broad range of torque from the L98 can be felt through a wide range, something you do not get with a single peak. This is the reason you feel the L98 down low. You are correct about the tubes tuning into a certian RPM range, but the large plenum and the tubes help with torque everywhere.

Testiculese

Another article citing 350 ft-lbs of torque for the L-98.
http://www.superchevy.com/technical/...n/viewall.html

Kubs

MK 82

The "hotcam" is an aftermarket cam.

Tom400CFI

This thread is getting frustrating.We were talking LT1 vs. L98 in this thread, which is 340tq for both. +5 lb-ft for the late L98 with manual trans and "free flowing" exhaust only. BOTH the LT1 and the L98 make about the same tq up to 2500. So both are "right there/immediate". You don't need to rev either to 4500 to get immediate throttle response. What you DO get w/the L98 is a midrange surge that you do not get w/the LT1. That is where the SOTP gratification is in the L98. I agree that this also makes the L98 feel like it's doing it's work with less effort -in most driving. Of course, revving it to 5500 is the opposite; there it feels like it's being murdered.

Stop light to stop light the L98 does NOT smoke the LT1 and any day at the drag track will confirm that both cars 60' ABOUT the same.



I think you have it backwards, Kubs. Look at the graph that aboatguy posted, again. The L98's tq curve is absolutely NOT "flat". Look at the thing. It's literally shaped like a mountain...PEAK! lol. That is what we call a "peaky" tq curve. Now look at the LT1 tq curve. That is (relatively)....FLAT. The "peak" is at ~4000, but as you can see, it isn't much of a peak.

I also don't understand your last sentence; Neither the TPI nor the LT1 have large plenums, and the "tubes" (in the LTR intake) definitely do not "help with tq everywhere". They "help with torque" only in the narrow range for which they were tuned to do so. Everywhere else, they hurt torque...again, just like tuned pipes on a 2-stroke. SAME Physics.


Bottom line is both motors were built with totally different philosophies; one was to focus as much tq in one place as possible, to get the most tq possible (which came out to 330-345 at the time), and the other was to spread as much tq as possible, as far as possible, (which came to 330-340 at that time), and extended the rev range another 1k or so. This resulted in a flat curve as nothing in the engine is tuned to "one" RPM. Technology (combustion chamber and compression) in the LT1 allowed for similar tq w/o resonant tuning, simple as that.

But back to "feel and SOTP", like I said in an earlier post, the PEAKY L98 tq curve is what gives a satisfying feeling result, just like that gutless, VAG 1.8t has, that every one who drives one, thinks is so "fast".

Testiculese

Partially correct but I suggest you do a review of "Wave Mechanics, and Wave Tuning, along with looking up how pressure harmonics work in 4 stroke internal combustion engines, in both intake and exhaust systems.

Heres a question for you Tom400CFI, can a normally aspirated 4 stroke V-8 engine achieve greater than 100% VE? If so what kind of intake system would it be using?

Tom400CFI

Thanks for the...ahem, "tip", but I'm pretty well versed in tuned intakes...and exhaust. Thank you very much.

Yes, an NA engine (4 or 2 stroke) can achieve greater than 100% VE. We both obviously know that. And of course we both know that it would likely be using a tuned intake AND a properly tuned exhaust. Of course those tuned parts would likely be tuned to work at an RPM far higher than 3200.

We also know that neither the stock L98 nor the stock LT1 achieve 100% (or anywhere near that) VE.

93 ragtop

There is a bunch of bad information being thrown around on this post. I have personal experience owning both L98 and LT1 vettes. I have raced against L98 of all types at corvette drag races. And Ill tell you. Assuming both are stock and both have a 3.07 gear, the L98 has no advantages over the LT1. The LT1 will be at least equal off the line and after that will walk away from the L98.
As far as different intakes making the L98 faster then the LT1? I don't believe it. Show one person that changed nothing but the intake and made it faster then a LT1.
And if you really want to see a stock engine LT1 perform to its potential, put a 2800 stall, 3.73 gears, and a set of drag radials on it and you can be in the low 12's on a good day, mid 12's all day long. For proof, go the drag racing section and look at old post of John Mackeys, or JPEE

Testiculese

Are you really?
Then you'd know the TPI was the 1st NA intake to achieve over 100% VE. 102% or 104% was the mark, I know this because reading it when I was in college back in the late 80's early 90s, is what made me really interested in the intake system. Will look it up in my old mechanical engineering books to give you a cite.

Google it and you'll get the right answer.

Testiculese

Put the same gears, stall and a tuned intake sized to 5.7l not the 5.0 choker thats on the L-98 and see what happens. I have enough torque with my 91 that my neighboors 2012 6.4l Challenger couldn't beat me off the line, and I got in front of him fast enough to pull over in front of him and let off my gas with out him having to change lanes. That was maybe an 1/8 or close to it, longer yea he probably would have crept by me and slowly increased his lead, thats not the point though,--------TPI cars are made for daily stoplight to stoplight jump off the line and pin you back brute accelleration, not the track.

Then theres the sexiness of the intake....LT's intakes just have nothing on it.