what are the differences between twin entry and single entry

[da_horse]

hi

i've recently bought a ct26 turbo and manifold, however it isn't a twin entry one, so i was wondering exactly what are the differences between the two? are there any benefits in gettin one over the other, is there any performance differences? when i eventually get around to putting which may be up to a years time as i'm goin to be busy finishing my final year, i'll only be running 7psi max, but i was just curious one their differences....


thanks

Huy

btw for a 1989 Camry 3sfe manual


this is what i have:

[alltrac165]

A twin entry is supposed to offer better scavenging and faster spool response. It pairs #2 and #3 on one scroll and #1 and #4 on the other scroll. This means that the exhaust pulses to the turbo are evenly spaced at 180 degrees apart on each scroll which allows for a stronger "push" on the turbine wheel. It also eliminates reversion from the outer cylinders to the inners and vice/versa which you find on a single entry with a short manifold such as yours(and mine, I have the '88 3SGTE which is single entry). You would find that reversion on any log type manifold even without a turbo, actually.

[lcarocha]

Right on the money.... There is a revision for the CT26 turbo where Toyota changed to twin entry because the housing started cracking because the high temps and pressures generated by the exhaust gases trying to enter and leave the turbo thru one entry.
Also bolt pattern was changed from the original four bolt one to the newer six bolt pattern and the housing was made stronger

[crazy_camry]

Originally posted by Da_HoRsE
are there any benefits in gettin one over the other, is there any performance differences?

you'll have your single entry CT26, i'll have my twin entry, and we'll race j/k

[da_horse]

thanks for the info guys, so from what you guys have said a twin entry is more efficient, however if i had custom manifold done, eg equal length pipes etc, it still wouldnt be as beneficial as the twin entry yeah? is it possible to get a different compressor housing that has the twin entry?


ta....

and hugh we'll wait til i get it done, then go up to sydney lolz....long time to go mate....but first hurry up and finish ur car...i'm eager to see how things go...

Huy

[crazy_camry]

Originally posted by Da_HoRsE
and hugh we'll wait til i get it done, then go up to sydney lolz....long time to go mate....but first hurry up and finish ur car...i'm eager to see how things go...

Huy

lol i want to see it done too, keep spending my precious little money on other things, besides that fusion 15" i'm getting, i've put a deposit down on that pioneers head unit that flips down to reveal a second face.

[alltrac165]

I think the biggest advantage is the split manifold for less reversion. A good aftermarket manifold with a single entry turbo will work great.

[da_horse]

thanks mate

[white90dx]

Originally posted by alltrac165
I think the biggest advantage is the split manifold for less reversion. A good aftermarket manifold with a single entry turbo will work great.

If the turbo is a true twin entry (twin-scroll is the other term I have heard), then you get a better spool and better top-end response. The turbo is able to act like it has two different A/R ratios (one for fast spool, one for high flow). Good stuff.

The twin entry has little to do with reversion. If you notice tha manifold has individual tubes, so it would be quite hard for the pulses would have very tough time reverting.

-Charlie

[alltrac165]

Originally posted by white90dx
If the turbo is a true twin entry (twin-scroll is the other term I have heard), then you get a better spool and better top-end response. The turbo is able to act like it has two different A/R ratios (one for fast spool, one for high flow). Good stuff.

The twin entry has little to do with reversion. If you notice tha manifold has individual tubes, so it would be quite hard for the pulses would have very tough time reverting.

-Charlie

Twin scroll is a bit different from twin entry or axially divided turbines. A twin scroll is as you described and actually has a valve inside the turbine to direct all flow to one side at low rpm for greater velocity and faster spool and then opens for greater flow at higher rpm. Twin entry is just a divided housing with no valve and generally symetrically shaped halves.

I have one of the manifolds in question, and while yes there are separate tubes, they are extremely short. Turbos exhaust systems tend to operate under a lot of pressure. On any two cylinders that fire one right after the other, the first cylinder to fire will still have an exhaust valve open when second one opens. Since the first cylinder has blown down to a pressure at least as low as what is remaining in the manifold, when the second one opens, the pressure will climb again and cause the exhaust to change direction in the first cylinder which has a much lower pressure. On a really short runner system like we're talking about, that higher pressure exhaust gas can go right back in the cylinder before the valve closes. There are two ways to deal with this. One (which was probably a side effect of searching for better spool response in this case) is to split the manifold into two pairs all the way to the scroll. This usually means cylinders that fire 360 degrees apart instead of 180 are paired together. That extra separation allows for the valve to close in the cylinder that fires first before the second opens which much reduces reversion. It is also supposed to provide a stronger pulse to the turbine which should decrease lag. The other way to reduce reversion is to have longer tubes before the collector. Like 10 to 12 inches or so. Possibly a lot longer if you are wave tuning. This means it simply takes longer for the reversion to get back up stream as it has to reverse the flow of a larger column of gas and the valve should be closed by then.