first of all if i get a down pipe and mid pipe i heard that your car starts to smell like gas. if this is true is it really bad and is there anyway to get rid of it. second of all is it true that twin turbos always spool up faster than single turbos even if they are ball bearing. if this is true can someone please explain thanxs

 

A downpipe won't make your exhaust smell like half-burnt fuel. A midpipe will. This is because the midpipe is a straight-pipe that replaces your catalytic coverter. Without a catalytic converter, your exhaust will be untreated. As a result, you will have much larger amounts of ozone, carbon monoxide, and unburnt hydrocarbons (the smelly stuff) entering into the atmosphere from your exhaust.

 

I'll have a crack at the spool up question. All you 1000 post experts correct me if I'm wrong.

The two sequential turbos in the stock setup of our cars don't spool faster ... they reach peak boost faster. This is because the engine’s exhaust need only spin one smaller turbo, then at 4500RPM's with all of the extra exhaust associated with the higher RPMs spin two.

A single turbo has to be capable of pushing more air, is larger that the stock twin's, requires more exhaust to spool and thus takes more time to boost or spool up to generate boost.

I know … it sounds like the single spools slower, but only because it’s receiving a smaller amount of exhaust given it’s size. If it was suddenly dropped into the picture at 4500 RPMs I don’t see why it wouldn’t spool up just as fast as a single at 2000 RPMs.

 

Stock SEQUENTIAL twins will spool faster than non-sequential. (parrell) This is same for Single Turbos. That is the beauty of the twin system. Good power at low rpms.

Usually single turbo owners don't really worry about turbo lag because of the huge amount of power they are producing when they do infact hit boost.

 

This is basically a case of semantics, 'cuz I was always led to believe that "spooling up" meant getting into the boost (building positive pressure) faster, which is where you start getting some real power to the rear wheels-- which is what Shabib67 is probably interested in. Which means yes, the stock sequential "spools up" quicker than the usual big single.

Also, the sequential setup begins spinning both turbos simultaneously (not the secondary later like you're implying), that is why it transitions so quickly to the secondary turbine. Otherwise, you'd still get lag, no matter how small the secondary turbine is.

Kento

 

the spooling depends on the pitch and size of the exhaust blades as well as the intake cartridge fins. size of ports relative to stock size, and if there are any modifications. time and temperature also play an important role in a turbo's ability to spool.

samller ones will spool quickly, mainly due to the smaller amount of mass that needs to be moved, and and the relatively small passages that the air will be traveling through.

there are some very quick spooling big singles out there, and yes, many of them are BB units, but the down side to them is that they can not be rebuilt...

 

The first couple of minutes after a cold start smell pretty bad until the main cat gets hot enough to work properly.

Shabib67: I think you need to spend a little more time searching and thinking before you post. Those "two questions that need to be answered" have been answered many times before.....like last week. I don't mean to pick on you personally but it seems like all of your posts have been of this nature. You're not the only one by a long shot but.....