Neither seems relevant or complete. L98TPI is [really] comparing his TPI setup to the potential for a MR (LTx) intake. That means 5k rpms isn't really the cutout. It's lower...probabably 4300-4500 rpm crossover to the MR making more power.

And, you can't "just" add/subtract cell on a spreadsheet to see which hypothetical engine will make the most power....unless that's ALL you care about. Yes, theory is nice, but it can't and doesn't say which accelerates when, how much, and in what rpm of each gear -- compared to the other.

For this hypothetical comparison, I wouldn't say 6500 is a valid rpm ceiling either. Because that's well above the typical LTx redline. Add'l support mods would be required to turn that sort of rpm regularly.

IOW, I don't see anyone coming to any agreement anytime soon.

That said, I like the idea of posting final drive torque for each gear (and 500 rpms) in a link as provided. Along with comparisons like the "10 times the Torque TPI Shootout", I think the addition of rwtq helps throw perspective on what you're really building.

Realistic time in each gear would be good too.

 

Snowmobile. 180 hp from .8 liter. CVT makes it work and keeps it at the HP peak all the time (at WOT).

Greggpenn, it is hard to tell what specific motors he's talking about. Apparently it's two from that article, but I don't know which one the "TPI" one is. I haven't sat down and spent the time to compare tq curves from the article to the tq numbers in the spread sheet to see what aligns.

But his spread sheet is the foundation for a good tool. One could "geek out" on that sheet if a while, if one was inclined to. I like to mess around w/that stuff some times.

 

The 2 intakes used in the spreadsheet are the big mouth manifold (tpi) and the MiniRam.

 

I have the big mouth (TPI) intake and the dyno sheet, which is located in my Photo Album L98tpi, has a similar curve to the big mouth curve from the article. Maybe someone that has done a mini ram can post their dyno and we can see if it resembles the mini ram curve in the article.

 

Of course it would. That's why the TPI shootout was done. Cam size might change the curves a bit..but generally the same. Looks like I underestimated the TPIS runner by about 500rpm after rechecking the 10x article.

The real question is what rpm are you comfortable with...More importantly where you get 525 ft/lbs for 2500rpms on the 250 ft/lb motor? What gear? What planet?

Mine makes more than most (for a 383) at 2500 rpms -- at the ground which is 350rwtq. The 10x article shows 400ft/lbs on an engine dyno. (fwtq).

Were you looking at a lower gear than 4th?

 

I know. The numbers coming at us are all over the place, from "which engine makes more power, 250 or 300 (it's 300...again), to some weird made-up numbers, to this article...all with references to his own engine, which we know nothing about.

It really doesn't matter. Then engine with the highest HP rating, MAKES THE MOST POWER (note that I didn't say force, though if it has more power, gear will create superior force, too). It can potentially do the most work, in the least time.

 

That's SO WEIRD you'd say that! It was really getting hard....You know, trying to figure out your true feelings on the subject!

I think we know plenty about L98TPI's engine. His profile and dyno tell a pretty good story. BTW...L98TPI, very nice TQ numbers -- especially for a 350!

 

I know it. Lol. I'm not sure that "feelings" are what drove my point though.

L98TPI's engine does look like a heck of a "fun time"...now that I went and had a look.

 

Was there really a 3 page argument/discussion on which engine creates more power between a 250hp and 300hp engine?

 

Alright, I admit I was wrong in my original assertion that the TPI was putting out more power. I was out of context in looking at torque as power output. So I did find the formula for power which is

Power= [ rpm/60 x 2(pi) x torque] / 550. Measured in ft/lbs per second.


Pwr TPI. RPM. Pwr Mini
404. 4000. 347
436. 4500. 398
452. 5000. 447
440. 5500. 487
457. 6000. 503
458. 6500. 507

I put all the values above for power at each rpm for each intake and used the torque values from the spreadsheet posted earlier. So from this we can conclude that the TPI puts out more power from 2500 to 5000rpm and puts it's max power out at 6500rpm. And the MINI RAM puts out more power over 5000rpm and the most power of either intake at 6500rpm where it produces 507 ft/lbs/s.

 

Must be for TPI shootout graphs. No one uses THAT size cam with longtube...so really the TPI rolloff happens sooner -- like the dyno on your homepage (garage).

Interesting to see it won't fall off with enough cam...though you gotta be losing [more useable] response on the bottom end.

 

Thank you. Now, do you still feel that
I was literally spoon-feeding you the answers, and showing you the math...and the above was your response; closed, condescending...wrong. I don't mean to rub salt in a wound, but I hope that you can now see why that was pretty irritating.

FYI, you don't need to do any math (other than maybe subtraction) to compare engine POWER when you have a torque graph or chart and are comparing tq #'s at the same RPM's, engine - engine; the engine with more tq (at a given RPM) is making more hp (at THAT RPM). So you are right that the TPI is putting out more hp below 5000 RPM according to the data. SAME gearing, it would accelerate faster than the LT1, up to 5000 RPM, in first gear. After that, shift points would move the advantage to the LT1. OR more rear gear on the LT1 would give it the advantage, everywhere (most likely -didn't take the time to do the math).

 

As an outsider, you were being pretty condescending too. Hard to accept attitudes like that sometimes....I'm just saying. Here your first paragraph really shows that down-talking attitude again.

Spoon feed? Really? I wouldn't have been as patient as L98TPI.

You also got something wrong in the second para. "it would accelerate faster than the MR (LT1) up to 5000rpm, in first gear."

Need to get that stuff right if you're going to go all "know-it-all"!

 

Sorry for the typo (TPI vs. "LT1"). I can admit when I'm wrong too, so...


You know, I may have been somewhat condescending but I was right, I took the time to prove it and show why, and I did wait on the "spoon feeding" comment (which BTW IS, what I was doing) until after I was told that I should "close my suck", and that I "can bash with bull5h1t"....etc. You see?

 

Ok--how you doing Tom...I am making max torque of 400 at 4000 rpm, and max rwhp of 400 at 6200 rpm.. So, what's going on here...

 

I would find it really cool if this turned in to a discussion of how to find ideal exit and shift rpm

 

Graph your power curve and find your RPM drop between gear shifts. Then overlay your RPM drop per gear shift over your HP curve and find the point where you have the most power under the curve, that will be you ideal shift point for each gear.

 

100% correct.

Most people do not understand why you would run a dyno somewhere around 700-800 rpm above the HP peak.... its too figure out how quickly the curve is dropping and if that forces you to shift early. Most are going to have an operational band around 1500 rpm, but is a variance based upon multiple things. (Gearing, stall, weight, tire height, transmission)

On the video I posted earlier below, you see the fella shifting at 7100 rpm and dropping back to somewhere around 5400 rpm.... that is a basically stock C6Z that makes his HP peak in that 6300 rpm area. Hence, his peak HP is like a nice little Hill or umbrella..... 800 rpm below the peak drop back and 800 rpm above the peak shift point... give or take a little. He can do that because HP doesn't drop too hard above the peak, thus average HP is best with those shifts over the entire area. As a note, he makes his torque peak at 4700 rpm. But, he is only there once for a split second in the first 1 second of the video. (below the curve torque primarily only helps you for that first split second when under wot considering you spend almost no time in that rpm range)

I would guess the gear you want coming out of an exit puts you in the front half of your rpm window.... in this guys case its mid 5000's.


Good conversation.

 

Found this shift calculator online and plugged in the TPI Big Mouth numbers from the article and below was the result;

http://www.bgsoflex.com/cgi-bin/shif...000&hp9=&rpm9=

 

Thanks, I have never really understood if I should use HP numbers, tork or some other calculation. skewing the solution to a slightly higher rpm (if possible) will keep the car in a lower gear a little longer. Laying out the HP curv over rpm drop is a much better idea than smiply shifting when you hear the rod bolts strech!