Twins and how they spool ?

[mcdaniel1]

Lets say a truck has a HX40 on it now. Plenty of black smoke down low. The 40 spools at the typical 1900-2000. If a big turbo where added to the truck would the twins spool at the rate of the single 40 or would they be quicker together?



I suppose this question would also apply to a HX35 and then adding a larger mate.



I realize that it also depends on having enough fuel to spin the twins.



Given that my example indicates plenty of black smoke down low, lets say that there is enough fuel for the sake of conversation.

 

[Jetpilot]

A truck that is running a single HX40 will spool faster than a truck running twins utilizing an HX40 as the small turbo. The same hold true of using an HX35, the twin truck looses some low end.



Doug

 

[Partyat33]

I agree with Doug, but it also depends on the big turbo. If you big turbo does not have a huge housing, it will spool very fast. But, that leaves you a little shy on the top end if you are after all out power.



Dennis

 

[mcdaniel1]

Thanks guys.

 

[Jim Fulmer]

If your 40 is spooling at 1900-2000 I'd say there is something wrong, that would make Twins spool at 2100-2200 or so... ... ... I'd hate that unless the timing was at 30.



Jim

 

[mcdaniel1]

Jim

my 40 does start to bounce the needle on the boost gauge lower than 1900 rpms. From 1900 and up is where the boost really begins to fly, say from 10psi to 40. I think what I am looking for is the off-idle lag, seat of the pants feeling. I am not particulary dissapointed in how my 40 spools, just don't want the lag to get worse if I go to twins. My truck does have big tires with 3. 55's so my 40 is operating at a slight disadvatage off the line.



right now I am leaning toward a 35 as the little one in my set just to preserve some of the off-the-line pep.



thanks for the input

 

[Jim Fulmer]

From 1900 and up is where the boost really begins to fly, say from 10psi to 40



10 psi at 1900 means it's in the game and that is fine, yes you will loose a little more bottom end going to Twins, I'd ask myself were I want to be in the HP game, you can take Twins with a 35 a long way if they are setup right... ... as a guess I'd say 600, after that you should go to a 40 or so on top, I took a stock 35-18. 5/3B-26 to 670 on fuel and it was HOT!



Jim

 

[mcdaniel1]

Thanks Jim.



Your words are reassuring.



600 horses... ... sounds nice