[Gmecm] TBI - TPI swap ??

[Rick McLeod]

I just lent out my authoratative book on SBC's, by Lingenfelter, but I seem to recall he dub'ded the TPI as a tow truck motor, meaning it made gobs of torque off idle to the limit of the runners at just under 4000, and from my seat of the pants w/ the 3 I've tuned, that is absolutely true. My Vette will run down the road at 1100 RPM quite happy, will pull hills, and all, cruises very nicely at 70+ knocking down 33+ MPG, since it's sitting right smak on the bottom 1/3 of the toruqe curve, it still pulls strong without having to downshift. I've not been in a TBI car that does that, but the TBI's gennerally will rev higher so are better on track either stratght or twisty. But stoplight to stoplight, give me a well tuned TPI and I'll twist axles with it.


----- Original Message ----
From: Per Lonnborg <perlon at passagen.se>
To: gmecm at diy-efi.org
Sent: Monday, August 28, 2006 12:11:04 PM
Subject: Re: Re: [Gmecm] TBI - TPI swap ??


dennysweet at charter.net wrote at 2006-aug-22 05:20:

>Tuned Port Injection is pretty impressive to look at but you cant get a lot of power >after 5500 rpm and you lose a great amount of 
torque on the lower end of the RPM >scale.

Chris Reynolds [red83brick at yahoo.com] wrote at 2006-aug-22 17:01:

>The problem with TPI is the runners are setup to resonate at around 3,000 RPM, >which greatly improves torque there.   The throttle 
response will be slightly better >than the TBI setup, but you will lose a ton of low-speed torque, which is everything >in a heavy 
suburban.

Hello!

I just want to ask again if the two statements above is "true" about TPI vs. TBI.
I know (and probably everyone else too) that a stock TPI will lose its power above 5500 rpm due to intake runner diameter and lenght, 
thats a fact.

But I was quite surprised that TPI also would lose torque in the lower rpm, compared to a TBI system?
Arent those long, thin runners perfect for low- and middle rpm?

/Per
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