throttle before or after turbo

Tom Sharpe twsharpe at mtco.com
Tue Mar 9 01:21:17 GMT 1999



Ferman C. Lao wrote:

> Would a set up like this work on an NA efi engine?
>  Throttle body
>  NA MAP sensor
>  turbo
>  intercooler
>  intake runners
> port fuel injection
>  aftermarket rising rate fuel pressure regulator
> Stock ECU
>   I've been toying with the idea for quite some time , but havent had the
> opportunity to try it out yet.  It seems to me that by putting the NA MAP
> sensor between the turbo & TB will enable it to always read vacuum only &
> there would be no need to change the MAP sensor or ECU to one that is
> capable or accomodating boost readings.  My question is aside from the oil
> being sucked out thru the oil seals, are there any other problems ?
> And will the vacuum produced in a such a way be out of range of the NA MAP
> sensor?  How about the rising rate fuel regulator? Will it operate without
> any problems in a setup like this?

If the throttle body is small (at all), the turbo will create vacuum on the
inlet (map) side and boost at the engine. I used a 650 Holley on a T04B on a
350 chevy to limit boost.

Also, it is very hard to get enuf fuel to the engine w/ RR pressure. Suggest
secondary injectors with an on/off switch. Most of the time (unless you have a
heavily loaded vehicle in the mountains), boost = full throttle.

Tom S





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