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1614 Views 10 Replies 7 Participants Last post by  Beaverboy
I have been reading and i was wondering what were the differences between the VJ-20 and the T3 turbos. I know that to use the T3 you have to get a manifold made for it or get one from BLT but what are the differences?

Trashknight / 91 Escort GT (With MX3 Seats and self installed power windows)/ 92 Escort GT (Almose done being fixed!)

[ This message was edited by: Trashknight on 03-03-2003 01:00 ]
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I BELIEVE...that Blade said T3 turbos are notorious for not boosting until like 5000 rpms? because they´re too large...don´t quote me on it. :-?
FUCK I hate the new FEOA boards....they keep loosing everything I write and everytime I type something new it gives me a "I need to wait 30 seconds" So now I have to retype 15 mins of writing again.

Okay, let me restate the quote:
I said, I had a roommate that had a 99 Civic EX (D16Y8) = 1.6L VTEC. He had a T3/T4 hybrid and because he was only a 1.6L it didn´t really spool till his VTEC kicked in.

Okay, now I need to remember how I said what the last time I posted.

Okay the T3 is a meaurement size, not a specific turbo. Many companies ripped off this sizing method from Garrett. And they actually make different ´sizes´ of T3´s. The housing is the same size but the A/R ratios are different. The tighter an A/R ratio the faster you can spool, however it will limit the amount of boost you can produce.

The VJ20 is technically an RHB5 VJ20. The RHB5 family is the most popular family of turbo´s for IHI (Warner-Ishi). RHB5´s have been used in everything from Scooby´s to Isuzu Impulses. The VJ20 part is the specific turbo, like a sub-measurement of the T3. The VJ20 is a 52mm compressor housing and I´ve heard they can produce up to 20psi on a spike, but I´m guessing they wont hold much over 17psi. That might be hoping for a little much too.

Anyhow, IHI´s are known for spooling quickly because their A/R ratios are really tight. I believe the VJ20 is almost equal to a T3 with a .40 A/R ratio (smaller T3).

However if you compare across the board...even though the VJ20 is slightly bigger then a 14G in a DSM (14G is pretty close in size to a T28 which is technically smaller then a VJ20) I believe the 14G will actually produce up to 22psi on a spike. This is all because of the slight differences in the design of the turbos.

Here´s where I´ll try to answer you question specifically: Because the VJ20 is made by IHI their flanges on the turbos are radically different from the T3´s made by other companies. If you have a VJ20 you can use the manifold from the 323GTX if you get a T3 the size of the turbo will be close, however you´ll have to have an exhaust manifold made with a custom flange for that turbo.

On another informational note: the 323GTR used an RHB5 VJ23 turbo. The VJ23 is 60mm (8mm larger then the VJ20) and has a ballbearing cartridge, so it produces close to 2BAR of boost and can hold the peak boost through out your rev range. :-]
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TheBlade, whenever it gives you that message just hit the back button until you´re back to looking at the window where you typed up your message. Even if your message isn´t still in that box you can hit the forward button and it will resend the same information (including whatever you already typed). :cool:
Like he said, there´s more to it than just T3. I had mentioned that turbo before (actually, I think I mentioned the T3/T4 which has a larger compressor housing attached to the smaller T3 housing) and TheBlade corrected me. A T3/T4 would be way too big, but some T3s should work. TheBlade is the expert here, I´ve only done a little research on it, so please don´t take anything I say about turbos as the final word.

I´m much more familiar with some old BMW 4 cylinder engines than any of the mazda or ford scort engines, so please bare with me. There´s a Canadian fellow, named Paul, who´s had much success turbocharging his 2.0L SOHC m10 BMW motor with a T3 turbo setup which he drives on the street and in road racing (as opposed to street racing). He´s made a site and makes a few comments about choosing the right size turbo for your application using compressor maps. You might find it interesting :-]
(PS: there are some videos of him on the track too)

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I have a fried that runs about 18psi on his 97 Eclipse GST with a Hahns Racecraft Super 16G. Its a ballbearing turbo. Every time he plays with people on the road he always laughs "ha ha, you spooled first" just because when he does spool he pulls so HARD.

So sometimes having a little lag can mean such a huge performance gain on the top end that you dont need quick spoolage. Although I can pull on him in first because I spool quicker...I am hoping to get my tuning right so I can prove to him that If I spool fist I can hold my lead if I can match his power to weight ratio.

04-03-2003 at 10:20, TheBlade wrote:
"ha ha, you spooled first" just because when he does spool he pulls so HARD.


Twin turbo, baybee...

Hey jason, I´d like to hopefully build a car in the future that is a nice little handler like the EGT, but would also make a decent commuter car. Thus, I´d like to have it start spooling at around 3500-4500rpms. Is this possible? Is that generally early or late to start spooling up?

I dunno because I´ve never had the chance to drive a turbocharged car hard...

And what do you guys think of turbo-ing a 1.8L BP with 133K mi on it?
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If you just want a commuter car for dicing and slicing through traffic, you´ll want a very low lag turbo.. ie a very small one. VW has been using some very small turbos on their cars for great effect. 90% of the torque is available from just 2000rpm and throttle response is great.. but the top end is lacking a bit. 3500-4500rpm boost is really better for racing apps where you keep the engine above that range all the time. Go to an autocross some time and watch the guy there with the big turbo in the [insert favorite import car here] who claims to make 600+ hp and then watch him lag his way around the course.

I don´t really see mileage as a good indicator of whether or not a car is boost worthy. Now, compression tests, engine noises and past care are better things to go on. Besides.. if you build a system for your engine, you can then start throwing some money into building a BP engine on a stand with lower compression and some headwork to throw in there when you do happen to blow up the old motor. :-]
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commuter....for that u want...*drumroll* A 90-96 fairlady 300zx twin turbo...ahhh, im nuttin just thinkin about that car. :-] brb, i need a tissue

Twin turbo, baybee...

[/TD][/TR][/TABLE] would work very good on a 4cyl

I haven´t decided on my dream turbo yet. I think the VJ20 is a bit small for my dreams hehe. But then again I am crazy enough to dream about a land speed record braking EGT.
twin turbo on a 4 cyl doesnt work so well (just review pasts posts).

Beaver hit it right on. Small turbo´s for driving around. Thats what I love about my set up, 60mph and just under 3k on the tach and I can nail the throttle and be at 4-5psi. Dont get me wrong, like any turbo whatsoever there´s a little lag but its like 1sec if that, but thats because of the wastegate being set at 6psi for up here in Prescott. If it were set at 10psi it would hit 5psi faster.

I can see why matt wants to go a little bigger then a VJ20 though, last time he saw my car it wasn´t handling the altitude in Phx at all...quite the embarassment on my behalf. But Matt, looking into finding a VJ23....or since you want to hit a couple hundred mph in your scort, maybe a full on T66 with N2O to help spool it? :-Y :-]
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You can do a twin turbo setup using what are essentially two motorcycle turbos (tiny) that will spool very quickly, but again, there are trade-offs.. like the extra weight and complexity that might gain you 1/8th of a second less lag time with a possible lower cap in top end performance.

Then there are the sequential turbo setups. One small turbo, one large sized one. The small one runs out of breath just as the large one begins to kick in. Subaru uses a sequential setup on their B4 Legacy (not sold in NA) with the same EJ20 motor in the WRX, but every report I´ve read about that car says "sure it´s fast, but there´s a dead spot between the turbo´s boost". There´s a sweet spot for each turbo, and unless you overlap them just right you´ll make for some nasty looking power delivery curves.

Overall it really isn´t worth the effort to twin turbo a 4 banger. Really, twin turbos are best used where you have two different cylinder banks and 3 or more cylinders per turbo.
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