You're right, I made a mistake. Cruising in the 25-45mph range is done in 4th. On the hwy, I'd at least be in 5th. So, I really should have mentioned the desire to double-down-shift vs triple-down-shift. But, the specific gear I'd use in those circumstances was correct. (2nd from 25mph-45mph and 3rd above that.)

If you look at the rpms for those ranges comparing my two intake choices, here's what you'd see in my 3.33 M6....

Gear-RPMs-MPH---SLP-TQ--HSR-TQ
2nd- 1600 20mph 276ft/lbs 278ft/lbs
2nd- 2200 27mph 333ft/lbs 311ft/lbs
2nd- 2800 35mph 430ft/lbs 382ft/lbs
2nd- 3400 42mph 477ft/lbs 412ft/lbs
2nd- 4000 50mph 487ft/lbs 438ft/lbs
2nd- 4600 57mph 472ft/lbs 457ft/lbs
2nd- 5200 64mph 421ft/lbs 455ft/lbs

3rd- 2200 38mph 333ft/lbs 311ft/lbs
3rd- 2800 48mph 430ft/lbs 382ft/lbs
3rd- 3400 59mph 477ft/lbs 412ft/lbs
3rd- 4000 60mph 487ft/lbs 438ft/lbs
3rd- 4600 79mph 472ft/lbs 457ft/lbs
3rd- 5200 90mph 421ft/lbs 455ft/lbs

In practical terms, here's what'd happen: Coming out of a turn (in the city), I'd be in 2nd gear. If I hit WOT, I'd have the same amount of TQ with either intake for 1/2 second. After only a 10mph increase in speed, the SLP/TPI shoots out to a 50ft/lb advantage. Until I hit 60mph, the HSR wouldn't even begin to match power. By then, it would be way behind. In the city, who in their right mind is going to continue accelerating past 60mph? I won't!

The issue is even more true for a 3rd gear romp at hwy speeds. From 45mph up to 80mph, the SLP has a huge advantage out the gate. Again, I'd gain over 50ft/lbs of torque using the SLP for 3rd gear acceleration on the hwy. (Read the TPI link Rodj provided and do the math -- if you don't believe me.)

I'm saying with 100% certainty I wouldn't want to TRIPLE-down-shift. In the city, I don't want to drop to 1st gear under 45mph or use 2nd gear under 65mph. BUT THAT'S WHAT IT WOULD TAKE TO LEVERAGE A SHORT-RUNNER INTAKE'S POWERBAND (including the HSR)!!! For a person who owns an automatic transmission, the argument should be IGNORED. (Since an automatic doesn't shift this "conservatively".)

Aurora gets what I'm saying. This thread is to confirm that the extra level of torque is usable. IOW, that it'll hook as described. Otherwise, I'd be open to using the HSR for the MUCH MORE RARE circumstance where I'd wanna see how fast I can get from 0-90mph. You know....20mph over the highest hwy speed limit.

Final note: Just to be clear, the numbers above are adjusted projections for crank power with accessories. There do not account for drivetrain loss.

I WANT TO HEAR IF ANYONE THINKS I WON'T BE ABLE TO HOOK/USE THAT EXTRA POWER IN THE GEARING/CONDITIONS SPECIFIED!!!

 

You might spin second but you definitely will not spin third....if that is the answer to your question.

My Callaway TT made 575tq to the rear wheels. It did not spin 3rd all the time, less often than it did. The smoothness of the road surface, temp of tires, and outside air temps all played a major factor. When it was cool out and I was getting a good cold air charge to the intercoolers I could blaze the tires in third gear. On an average 80 degree day it didn't. Second was always a lost cause at WOT.

 

Hey Gregg, I'm really curious to see how the 383 turns out. I know that in my car, as I drive alot in the way you're describing, that when I dwn shift from 4th to second and stab it, I can set the ASR off for a second. I'm running the stock 3:45's. This of course with the Sumi's on the rear. I also really rarely have to down shift at all to get pass someone on the highway. When I do, the rear hunkers and it launches. The factor you haven't mentioned is that new dual mass you got there. That will keep some of the ridiculous out of torque when downshifting.

Considering you already have both intakes, either way you go, there's not much of a gamble. But if it were me and looking for streetable torque without too much concern for top end breath, I would start with the TPI, as they are more known for low end performance. I mean, if you want something more, the switch won't take but an afternoon.

Of course when describing "usable torque" I always have to figure in how well fortified we are with public safety agents in our neighbor hood. (I'm actually not complaining, this is a good thing really)

 

Too much torque is like too much sex.... After having a decent running Corvette a stocker feels LAME in comparison.

 

Greg,
I am not sure what your goals are, maybe you do not want to rev the engine higher then 5500, maybe you do not want to spend money on gears? You need to rerun your calculations and figure out the torque to the rear tires at each MPH point chosen for your discussion (include the transmission gearing and rear gearing in the calculation). If you run the higher RPM intake (HSR) and change the gears to 3.93 the car will be faster in almost all conditions (a very small window does exist between gear changes where the 3.33 ratio has a slight advantage) because there will be more torque to the rear tires with the gear ratio multiplication. If you look closely at your engine torque outputs with the SLP runners and the HSR you will see that the max difference is 12% in torque, the gear ratio change between 3.33 and 3.92 is 18%, the end result is for any given RPM the HSR with 3.93 gears will put more torque to the rear tires and have more acceleration. Even if you decide not to change the gears the higher power band of the HRS will allow you to change gears latter which will allow the HSR to accelerate longer in each gear and in effect end up with more torque to the rear tires at certain times in the power band. If you only want to accelerate from 20 MPH to 60 MPH on the street in second gear and do not want to change rear gears then the SLP intake is your best bet but the car will be faster with the HSR and 3.93 gears in almost all conditions.

 

Yes if this is the HSR curve you need to be shifting up past 6500 to get the benefit of additional horsepower..horsepower peak is at 6200rpm ..if you do not want to rev above 5500 then the HSR would not be what you are after .reminds me of another thread on the forum evaluating an LT4 but shifting it at 5500

 

You guys are catching up!!! The HSR is not what I "need" for a street intake but represents a great backup plan -- if I learned that traction (esp in 2nd gear) would be a significant problem. I have done my homework, considered carefully the way I'll use the car and where I want power. (This thread is me making sure I don't end up with a total tire-shredder in 1st and 2nd gear -- though I know it's well within range of EITHER intake if that's what I'd try to do. I actually want it to hook at WOT.)

The graph below is something I did a long time ago. The dotted lines show how my SLP intake might compare to the HSR. (Obviously the other lines show an HSR vs a stock manifold on a 383.)



I've also (graphically) compared this power (esp torque) level to LS2, LS3, and LS7 cars. Even in HP, it'd be comparable to an LS2/LS3. Midrange torque is WAY above the LS2/3 cars tough. In mid-range rpms, it should exceed LS7 torque as well.

(So, I posted my question about 2nd gear traction in the LS7 forum. One poster responded (who was a tiny bit touchy comparing C4's to C6's ), but he said there was no major problem in his car.)

 

OK, here we go....my car dynoed 345 ft-lb of torque and I have 4.10 gears....so in first gear rear wheel torque=345*2.68*4.10=3790ft-lb.

This will smoke my street tires but the drag radials usually stick...

in second gear rear wheel torque =345*1.80*4.10=2546 ft-lb

This will not smoke my street tires



So with your setup assume 487 ft-lb of torque and 3.33 rear gears

In first gear rear wheel torque=487*2.68*3.33=4346 ft-lb

so in first gear I would expect you would really smoke a street tire

In second gear rear wheel torque=487*1.80*3.33=2919 ft-lb

so in second gear it looks like with good tires you will stay hooked just fine..

Hope this helps.....you are going to have one really great street machine...



BTW I think tires themselves represent a huge variable in their ability to hook

 

 

Great post LT4Bud. Out of curiousity, at what force do you consider tire traction borderine? (Using the multiplication techique shown above?)

And, to be clear, the 487 number is only adjusted for exhaust and accesseries -- not drivetrain loss. (This was my attempt to compare my projected results to the LSx platforms -- and how the factory rates their cars.) So, power to the ground will actually be even lower than your example.

The bad news is I like to buy cheap Sumitomos. The good news is I'm running 11" rears with 315/35s.

The only other thing I can think of to provide some clarity is the reason I'm reluctant to downshift to 1st/2nd vs 2nd/3rd in the conditions mentioned above....

If I were to select the lower gear (and effectively drop 3 gears), I'd have to rev the motor to 3k rpms or higher. If I were doing it in a big hurry, I suspect it would be fairly simple to blow past the matching point -- and end up with a 400ft/lb rev and dump. IOW, it would be much easier to make a mistake and sling 3400lbs of metal around. And, this would pretty much be true with either intake.

By contrast, with the double-down-shifts described, matching rpms would be around 2k rpms -- which is just below where the real fun starts with either intake. For someone who won't be practicing speed shifts/racing all the time, this has to be an easier option w/o giving up much of the potential for fun.

But, really it's not a race for me. I'll be driving the car exactly like I did before -- just with alot more ummph. And, I'm shooting for the "right" amount of extra torque that provides maximum fun without going to a single down shift territory!

 

Greg,
The bottom line is in most conditions you will not spin your tires in second gear rolling on the gas. Even if you do lift a little until you get traction. My six speed Firebird sometimes spins the tires in second gear and it has 480 FT/LBS of torque at the engine as installed in the car with 3.91 gears and street tires.

 

By the same token, he could pair a 3.93:1 gear with the SLP runners, and then it would have the advantage over the HSR with the same gears.

Since he is saying he will not vary the RPM range no matter the intake, I don't see where he needs to bother with the math about wheel torque.

Each intake will be in the same RPM window, and in the same gear at any given speed. So whichever makes the most torque in the RPM window he will be using, that will be the "better" one.

To me it seems like people are getting hung up on the criteria he is using. And I agree, it is not what I would use. But it is what it is, his constraints are he won't shift, and he won't use more RPM. So with that, the SLP runners seem to make more sense.

To your original question Greg, what are you getting after in terms of a decision? If everyone said "you'll blow away 2nd and 3rd with that much torque", would you pick a different intake to intentionally lower the torque?

 

What does your car do now if you let it hook up in 1st, then punch the gas? You can easily do the math to see how your new setup in 2nd will compare, and then have a real data point you are familiar with. I don't know what you've done to your car to punch the numbers, nor do I know how your car handles 1st gear.

My car makes 350 lbs-ft at the wheels, and I have 315 GS-D3's and stock gearing (3.45:1 rear). In the summer, I can roll into 1st and hammer it just fine. It sometimes breaks loose a bit around 4,000 or so when the torque peaks. But it's not all over the road. In fall/winter, the tires are much less grippy and the engine is more torquey. It will definitely blow the tires away all over 1st gear.

 

You need to understand that at any given road speed you will see different RPM with different gears. The SLP set-up does not make as much torque as the HSR at higher RPM so you cannot gear it the same because it will be out of its power band and will have less rear wheel torque then the HSR and 3.93 gears. Torque at the rear wheels is what really matters and if you sit down and figure out the torque at the rear tires at any given speed you will see what I am taking about. The HSR with its higher RPM potentail can use steeper gears to increase the rear wheel torque vs the lower RPM SLP set-up with the 3.33 gears. If you are going to restrict the HSR with the same RPM range as the SLP set-up then the SLP design will offer the most potential; but if you use RPM and gear, the HSR set-up will have the most rear wheel torque at most conditions (which means highest acceleration). This include the 20 MPH to 60 MPH sprint that Greg is concerned with. With that being said either set-up will not have too many issues with spinning the rear tires in second gear.

Use the transmission gearing, rear end gearing, and engine torque, to caculate the rear wheel torque and any given MPH. This will show why the higher HP and RPM combination will accelerate the fastest. The gear ratio's of the ZF are 2.68, 1.8, 1.29, 1, .75, and .5. I am not recomending a crazy RPM combination, use 6000 RPM for the HSR and 5500 for the SLP set-up and you will notice that power under the curve with the HSR and 3.93 gears is higher with the HSR design which will provide the most acceleration.

Since Greg has both intakes I would recommend the HSR with 3.93 gears since it will provide the most acceleration. With that being said I am not sure what his ultimate goal is so I am anly providing information and he can make up his mind on what he wants to do.

 

Just wanted to say

This is a FANTASTIC thread.


Not everyone wants a high(er) RPM machine, so intakes like the HSR may not be the best choice. It is great to see a real discussion vs. the standard short runner is faster, no further discussion....

 

EXACTLY. And really, I have said it in this thread.

And, while you might say "WTF" in response, it just means I'm actually open to seeing/using their higher rpms on a rare occasion. For example, if the SLP was too torquey for a 383, I'd use the HSR and do this....

HWY entrance ramp full-out launch: Turn the corner onto a ramp and slow way down, dropping it into 1st gear. With a WOT run I'd shift just about 6k rpms. That would land only a couple hundred rpms below the torque peak in the next gear (as a racer would want). By the time I hit redline in 1st, I'd be going 50mph, 72 in 2nd, and 93 in 3rd (at 5400rpms).

The scenario would be fun too, but realistically more rare than the other two that I'm targeting. While it's also true I could drive out in the country and do the same, that's very unlikely. Going to a track to try my hand and getting good speeds/times is also not in my plans. (Though it might be fun -- just once.)

This, my friends is about building something that rivals modern day street cars. Or even something that feels even stronger. If I'd end up about where new Z06 cars are at (at least for short bursts), that has to be fun/impressive.

In appearance, the car has been modified/customized. As with more expensive "resto-rods", a certain level of "fun" power is usually added to sweeten the pot. That's more where I'm headed with this. Some day if/when I decide it's time to sell, having a car that pulls like a 600hp 427 will be more impressive (to a non-racer) than one that pulls like a 500hp 396 (even if it's faster).

As for the gears.....Since it's a grand ($1000) to swap out a set, that's not likely to be in my future. Though I admit 3.73s/3.93s would rock at the track, and retain most/all of the torque on the street, I think 3.33s provide something else. And, that is the ability to get rpms down on the hwy for some good old fashion mpg.

Before the build, my mpg was 30mpg on the hwy. Since I'll be getting a new job sometime in the (hopefully) not-to-distant future, I have to allow for the possibility that more hwy time might be part of the equation. Since a tpi hits 100% VE at lower rpms, I have to conclude that it would get the better mileage.

 

GREGGPENN
IMO it would be in your best interest to talk to GRUMPY and or a few others on DC vettes that have done the HSR. I think playing around with the LTR setup is old and and unsatisfactory technology.

The HSR kicks in before the MR, and has torque to compete with a SR and more HP. I think you might be disappointed with your LTR ideas.

I was going to do the HSR before someone backed out of buying my SR. I think it is a very competent intake all the way around. And you don't need steep gears for the HSR.

good luck

 

Actually, I've talked quite extensively with a couple of people with comparable experience. (Yeah both like the HSR option better, though one would pick the FIRST over both.) But, those guys are way more experienced with automatics and all-out racing. In that arena, I have NO doubt the HSR is a FASTER intake. ***

But you only have to look at the numbers in my post at the top of this page to see why it's probably not as fun for my most common situations.

That's why the whole point of this thread was to determine hookability. It's the one question that racers don't have as much experience with -- especially when you're running it around town and shifting like I do. IOW, it's the kind of situation where there's more room for torque and less need for speed.

I'm afraid I might be disappointed -- if the torque isn't high enough! After all, instead of a time-clock, that'll be the real measure of success for me.

Edit***: But it's only faster if you run it in lower gears to the rpms Bjanuski eludes to in his post. And, BTW, what he posted in something I do understand. It's the specific rpm ranges and gearing listed in the post at the top of this page that show where/how the TPI can gain a specific advantage. IOW, the SLP would be faster when limited to THAT situation (rpms/gears). Really, I'm building for the most common situation vs the fastest track car. (If I ended up using the HSR -- in the same exact way -- I'd actually go slower unless I went to higher rpms in a lower gear. Even if I installed higher gears, that fact (and my driving style)wouldn't change.

 

Aurora,
Actually, I left out a couple of less important details that pertain to my decision-making process.... While they have less to do with performance, they were on my radar.

The HSR would be world's easier to swap out injectors -- if/when I had problems with them. The HSR could me more appealing upon resale since it's 1/2 second faster -- if raced. And, the HSR just an easier intake to work on, from the injectors, to the thermostat, to complete r/r. And, many people like it's appearance because it's a hirise intake.

Finally, I'd be less worried about my (new) clutch/DMF setup wearing out with a powerband that was smoother like the HSR has to offer. More torque would obviously "hit" a DMF harder and could wear it out faster. But, my modest driving style might not make this issue a factor. (IOW, I'll be smoothly applying power vs thrashing it.)

Personally, I like the SLP's appearance better. What you see pictured on the first page really does look nice in person. To even up the comparison, I might break out my polishing stuff and hit the plenum of the HSR within the next few days. If both units were polished, I might not feel as strongly about the SLP.

OTOH, those torque numbers I posted are pretty compelling. Using the HSR to gain maintenance advantages while using it with rarity to hit higher speeds (and rpms) don't seem enough to change my mind.

It's the traction issue that could make the bigger difference.

 

All I can say is I understand about torque at the wheels and whatnot. But he's been clear about the RPMs he would turn. So the HSR will make more torque at an RPM he will never see, regardless of rear gears.

With the constraints he has laid out, the rear gear is irrelevant in-so-far as comparing intakes. He could change the rear gears with an SLP intake the same as he could for the HSR. Both intakes have the same "effective" RPM range, because of the owner's refusal to rev the engine.

Edit: Nevermind, now it sounds like occasionally he'd use the higher RPMs...