I've heard that a TPI engine is quicker from a dead standstill than an LT1 but that the LT1's torque curve is less making it faster in the 1/4 mile, Is this "just a pile of Horse puckey" or is there some truth to it?

 

I dont know if there isnt much LT1 knowledge or what on this board, but I have a similiar unanswered question, will a Ported/Siamesed Plenum, SLP siamese runners, and TPIS Big Mouth Base flow (A lot less) ( A little less) (As Much) ( A little more) or (A lot more) than the LT1 intake.

 

here is the way i understand it you wont get the tpi to flow like the lt1 its not so much how big your base and runners are but the length of the runners tpi jus doesnt do much over 5000 rpm i was a little none beliveing of this until i swapped to the lt1 with the tpi i rarely hit my rev limiter "6000" but now with the lt1 it took me a little while to get use to how fast 6000 comes now thier for a while i was always hitting the rev limiter it comes so quick now i had a completely upgraded tpi im very happy with the lt1 it gives you alot more potential for future mods if you think about it have you ever seen a after market lt1 intake? i havent there no need for it if im wrong im sure ill be corected jus my.02 worth later:lala: :hail:

 

true...holley has an aftermarket intake for the LS1....:lala:

 

I saw that holley Intake for the LS1 just yesterday and even asked why anybody would buy it

Aftermarket LT1 bases never flew, guess why? They flow like a son of a gun stock.


TPI is a tuned design, you make so much torque at such low RPM's with it for obvious reasons, The narrow long runners provide tons of runner volocity, but when the engine is trying to spin high rpms and is begging for air the narrow long runners just can't get enough into the cylinder to get the job done and the engine runs out of breath. There's also the "Tuned" aspect where the column of air rushing towards the Intake valve gets abruptly stopped by the valve snapping shut its theoretically supposed to pulse backwards and return to the valve again when the valve opens with additional energy.

LT1's are a "Detuned" setup, its nothing but pure flow, and the reason they do better in the quarter mile but maybe not the 1/8th is because you can shift them almost 2,000 RPMs later than TPI engines.

So in picking what you want, pick what you want to do with the car. TPI can be a blast on the street, and you'll think you're king shlt because of all the races you win light to light, but first time you get a TPI engine on the track and you launch spinning the first 3 gears, then you're out of gear and engine half way down the quarter and the car next to you walks you like you're standing still you start to reconsider on the TPI thing, at least I did

 

with the lt1 intake on my 383 i cant tell a diff around town the tourqe i had with the tpi is still there im sure the 383 helps out i truly believe a 383 and lt1 intake are perfect for each other

 

You can get a TPI intake to flow like an LT1 intake, but never behave like one.

With the right porting etc., you can achieve the same flow numbers (cfm) with a TPI as you can an LT1, but that is only static flow.

The dynamic flow that is present in a running engine is completely different. As tpi_roc mentioned earlier the pressure wave caused by the intake valve closing sends a pulse back towards the plenum. When it hits the plenum it is reflected back towards the intake valve. At certain rpms, this pressure wave will hit the intake valve at the exact time it opens, and kind of acts like a little supercharger. Since the pressure is higher than normal it forces slightly more air into the combustion chamber. The downfall of this is that if the intake valve opens when the pressure wave is heading towards the plenum then the pressure is less than normal and it has a detrimental effect. This is why the TPI shines in the midrange, but sucks at the top end.

And as you can imagine, having a shorter length runner means that the wave has less distance to travel and will return to the valve quicker, which is good for higher rpms. This is how the LS1's are setup. I believe their intake runners are about 14" long, and the "tuned" powerband is from about 4750 - 5750, where you spend most of your time during a drag race.