ct-26 tt question

[OneJoeZee]

I don't think fitment would be a problem. My turbos are bigger than CT26s and it's fine.

Yes, it's a 1J but you get the idea.

A TT 7M setup would require a lot more trouble than it's worth, IMO. You'd most likely have to go to an FFIM if you haven't already and fab up every part of the kit.

Just go single.


My TT kit was 100% bolt on and took less time to install than it was to take off the stock twins.

If I had been piecing together a kit, I would have just gone single.

 

[ATL88Supra]

a ct 12 ct 26 set up would work but it would still be kinda crapy

 

[tubbie]

You guys are funny.... :rofl:

You CAN fit two ct26 in the supra. You just have to set the rear one higher then the front if you are using the stock elbow. Plumbing is a nightmare though...

A single turbo IS much easier and makes the same or more power, but the BLING of opening the hood and saying TWIN TURBO..... :evil2:

Spooling the ct26 with 1500cc is no problem. A couple guys I met in NC with Honda 1.6L are using the ct26. Spools 8psi at about 3800rpm.

 

[Datsrboi]

Small twin turbo setup are good for circuit track. Faster boost.

 

[OneJoeZee]

Small twin turbo setup are good for circuit track. Faster boost.

Gotta source to back that up?

Because I don't believe you. I know why but I'd like to hear what you think.

 

[Datsrboi]

Gotta source to back that up?

Because I don't believe you. I know why but I'd like to hear what you think.

Well don't small turbo has less lag? Less lag means faster spoil for quicker response at circuit tracks where pulling out of corners are pretty important I believe so. Thats what I was taught at some shops around my area and at the track with the older dudes.

 

[OneJoeZee]

Well make sure to keep your definitions of lag, spool, and powerband straight.

I didn't know what "Faster boost" meant in your post. It's not as simple as saying faster boost. That's too vague.

These two posts should help you out.

All right guys, we need to separate lag/spool from power band.

Lag/spool is basically the time from going WOT to achieving target boost. This assumes you are already in the power band (IE stabbing the throttle at 2krpm and waiting 20minutes to get to 6krpm with a GT55 does not count). This would be like going full throttle at 5krpm with a GT40 and waiting a second to reach 20+psi.

Power band is an entirely different subject. This to me is the engine speed range which provides sufficient turbine power to achieve your target boost. So, a GT40 may have a power band from 4-7krpm and a GT47 may be from 6-9krpm (engine speed).

The reason I make this distinction is a single turbo rocks in one aspect and twins in the other. All things being equal (which obviously is never the case, but stay with me) a single turbo will always be more efficient than two. Now, that isn't to say that every large turbo is better than every small turbo, but if you had two that were designed and manufactured using the same practice the larger turbo would show superior efficiency.

That being said, the more efficient a turbocharger is and the larger the powerband. So, a single turbo capable of flowing 800hp will have a larger powerband than two turbos capable of flowing 400hp each. The more efficient single turbo will also require a lower expansion ratio which results in a better engine delta P and (finally) and greater engine VE (more power).

Now, when we talk about spool it's the opposite. The larger single turbo has significantly more inertia and will take more time to reach the target boost. How much more I can't say, but it's simple physics. I don't think this requires much explanation so long as everyone understands my definition of spool/lag.

If we take this a step further and look at just an inline 6 (like our beloved 2jz) it all becomes clear. Fundamentally, a turbine is most efficient under steady state (no engine pulses). The best we can do is to have as many pulses as possible to limit that time gap between them. Further, it is beneficial to have a twin scroll (divided turbine housing) as this eliminates the possibility of cylinder to cylinder scavenging and helps to get as much of the exhaust energy from the head to the turbo. An inline 6 is the perfect platform for just this. With a standard 4-stroke engine the most number of cylinders you can have feeding a single collector (with no chance of cylinder to cylinder scavenging) is 3. If you have 4 there can be times when two exhaust valves will be open at the same time. A divided 6 cylinder is perfect for this.

So, in short, if you want the most power go single. If you want the largest power band, go single. If you want the best response at corner exit on a road course, go twin.

Daniel

And

No worries socalguy, I was not talking about you. Doing a straight comparison between a single vs. twin is going to be VERY difficult because of the number of factors involved.

When comparing ultimate power it's really determined by two things (if we assume the same 2JZ engine at a given speed): 1) Boost & 2) VE.

If we assume, as we should, that you are operating at a fixed boost level, then VE is all we care about. Since we are talking about a given engine, we don't need to worry about head design, cams, intercooler, etc. It comes down to engine delta P. A single GT4088R can flow ~70lb/min. A single GT28RS can flow ~35lb/min. So, using two of them should provide the same potential. Meaning, the compressor(s) can provide the same maximum amount of flow.

So, everything else being equal, both setups would make the same power. This brings us back to the VE stuff I was talking about. The twins will require more energy because they are less efficient. This will raise the backpressure on the engine and hurt VE. So, you wont make as much power and you will make it later.

Below is a ROUGH match I did. You can see that the twins spool later because of the lower efficiency. I assumed the same VE for both cases (and BSFC) so that is why the power number are line for line in the upper rpm. The max boost line on the twins is lower because the compressor map I was using didn't go to the higher pressure ratios so I kept the boost down. As I said, this is rough. I don't think you'll find a GT4088R that spools that quickly in reality which probably means some of my VE assumptions were a little....optimistic.

Daniel

HTH