Reading my books on the subject I decided I needed a pair of T3's for my V12.
When I kludged the twin turbo set up for Chump car racing I used a pair of T2's out of Saab's but they were limited and the most boost I ever saw was 6 psi
Now I'm looking seriously T3/4 hybrids but I'm feeling I'm being too aggressive. I'll just blow the surplus boost out the waste gate. Or is it that I won't get the boost in the first place.
This is too big.
But yes, if the turbo is too big then it gets really laggy. It may also fall to the left of the "surge line" on the compressor map, where the compressor wheel cannot produce stable boost at too low of an air flow rate.
You just need to do some math. This has some good info.https://www.enginelabs.com/engine-tech/power-adders/understanding-compressor-maps-sizing-a-turbocharger/
Is your jag going to be a 5.3L, a 6.0L, or something else? I would probably research what turbos others are using for engines slightly larger than half your engine size at the pressure ratio you want.
In reply to JBinMD :
There is almost no one doing turbo's on Jaguar's. One guy in Australia but he doesn't do anything except show pictures. My thinking is he has it done for him.
To answer your question. It will be a 5.3 liter early Flathead. With 7.8-1 pistons. Its's a Heron head design. That is the combustion chamber is in the piston not the head. The result is it's a pure Hemi with excellent flow and swirl properties.
The Japanese are very big on this T3/T4 hybrid making astonishing numbers for little 4 cylinder engines. So much so it's the best selling size and the price for good usable Brand new in a box is around $100. Now they don't have all the features the $1700+ dollar ones do. But as long as boost stays under 20 psi they seem to be reliable enough.
Racebrick said:You just need to do some math. This has some good info.https://www.enginelabs.com/engine-tech/power-adders/understanding-compressor-maps-sizing-a-turbocharger/
I've read a lot of the same thing. I've got several books on the subject and I listen to anyone not doing Monkey see Monkey do type work.
Years ago I found a good chat room where people actually took flow numbers, size, goals etc. and based their opinions on that data. The trouble is it quickly devolved into one high tech bit of trivial arguing with another. As if we all have $15,000 to spend
codrus (Forum Supporter) said:This is too big.
But yes, if the turbo is too big then it gets really laggy. It may also fall to the left of the "surge line" on the compressor map, where the compressor wheel cannot produce stable boost at too low of an air flow rate.
Yep. Too big. But I'd accepted the T3 with a .59 housing as right for me. Trouble is they don't seem to make those. Neither Amazon or EBay had cheap T3's it's been replaced with T3/T4 hybrids. As if we all are out to break the Dyno.
I'm going to run a small 7875 on one of my 5.3 ls's....
Anything worth having, is worth having to excess.
This is tricky, and all has to do with displacement and powerband at the highest levels. Remind me what your displacement is, valve arrangement, and max rpm and where it makes peak tq usually.
For reference I tune a stupid amount of 2.8-3.2l six cylinders and the smallest thing we use are T3/T4 hybrids with .82 turbine housings (or similar GT series turbos) but mostly full T4 with .58 turbine housings at smallest. WIth the larger T4 exhaust wheels they are similar to the T3 .82 in spool and total flow. The race cars usually use a T4 .96 or 1.06 hotside but you aren't making jam till 5500 and revving it out to 8k+ which is hard on the motors.
A single 78/75 with a T4 housing is VERY popular with the 4.8/5.3/6.0 crowd. Fast spool, good power.
I have a billet 78/75 for my 6.0 LS. I hear it spools like a light switch on a 6.0, and can easily put 650+ to the wheels.
T3 or T4 or T5 is just the size of the housing - there is more to turbo sizing than that. A bigger housing can produce less back pressure, which is always good.
JBinMD said:Is your jag going to be a 5.3L, a 6.0L, or something else? I would probably research what turbos others are using for engines slightly larger than half your engine size at the pressure ratio you want.
I was about to say this. The Ford 3.5 twin turbo uses either 2 K03 or 2K04 turbos to make 365 or 420 hp. A lot of guys are making 325+ hp out of the VW 2.0 TSi engines with a K04.
The T3 sounds pretty small:
"The T3 is the smallest family of turbochargers that Turbonetics offers. Perfectly sized for applications under 2 liters, the T3 line-up starts with the 150 HP 35 trim wheel and goes up to the 325 HP Super 60. T3 compressor wheels are efficient up to 22 psi. "
The T3/T3 sounds like it would be perfect:
"The Garrett T3/T4 Hybrid race turbo is the next step up from our street turbo. These high-boost turbos share the same low inertia and T3 turbine wheel and T4 compressor to make this the best choice for those wanting to make 300-500 horsepower. The high-boost turbo is designed to spool fairly quickly and can support up to 500 horsepower. The high boost turbo is a Garrett TO4E 50-Trim compressor wheel with a stage 3 .63 AR turbine housing and .60 AR on the compressor side. T-3 flange, 4-bolt turbine outlet. If you're ready to make some big power, this is the turbo for you! Upgrades such as ceramic bearings are also available. Turbo housing features a 3" compressor inlet, and a 2" Turbine outlet."
https://www.lceperformance.com/Pro-Turbo-Garrett-T3-T4-Hybrid-Turbo-High-Boost-p/1071004.htm
I wouldn't be too worried about a T3/T4 being too big. Lots of type 1 VW guys use them on <2L setups. And they're cheap enough that if you don't like them, you can sell them off at almost no loss and get a pair of T3s that should be a near direct replacement as far as fit and everything.
Not to make things more complicated, but along with boost levels, you should consider your target rpm range too. But that's not everything, as turbos are responsive to load too. The T25 I was using initially on my 1.6 VW was an absolute pig. No boost in 1st, I'd get 6psi at 6k in second, but I'd get 6psi by 3400 in 3rd. It would have been better if the car was heavier but that's just stupid so I eventually put a T15 on it.
In reply to barefootskater (Shaun) :
That's remarkably good advice. These aren't for a street car and in racing I never got below 3500rpm and most of it was between 4500 & redline.
CAinCA said:The T3 sounds pretty small:
"The T3 is the smallest family of turbochargers that Turbonetics offers. Perfectly sized for applications under 2 liters, the T3 line-up starts with the 150 HP 35 trim wheel and goes up to the 325 HP Super 60. T3 compressor wheels are efficient up to 22 psi. "
The T3/T3 sounds like it would be perfect:
"The Garrett T3/T4 Hybrid race turbo is the next step up from our street turbo. These high-boost turbos share the same low inertia and T3 turbine wheel and T4 compressor to make this the best choice for those wanting to make 300-500 horsepower. The high-boost turbo is designed to spool fairly quickly and can support up to 500 horsepower. The high boost turbo is a Garrett TO4E 50-Trim compressor wheel with a stage 3 .63 AR turbine housing and .60 AR on the compressor side. T-3 flange, 4-bolt turbine outlet. If you're ready to make some big power, this is the turbo for you! Upgrades such as ceramic bearings are also available. Turbo housing features a 3" compressor inlet, and a 2" Turbine outlet."
https://www.lceperformance.com/Pro-Turbo-Garrett-T3-T4-Hybrid-Turbo-High-Boost-p/1071004.htm
I used a pair of used T2's on my kludged up V12 XJS using a FMU to manage my fuel and the cold start injector near 5500 rpm. For Chump car racing.
What I liked is the power didn't ever seem to "come on" it just was there. Some of that was the conversion from automatic to manual and some was the lighter weight but there was a serious increase in power.
In reply to SkinnyG (Forum Supporter) :
plumbing for one turbo to two inlets on each side would be a nightmare with no space.
The difference is Jaguar doesn't have one throttle intake. It has two. One on each side. The engine compartment is tiny because a V12 is only 22" from side to side including the exhaust manifolds. ( the advantage of a 60 degree V over a 90 degree V )
Paul_VR6 (Forum Supporter) said:This is tricky, and all has to do with displacement and powerband at the highest levels. Remind me what your displacement is, valve arrangement, and max rpm and where it makes peak tq usually.
For reference I tune a stupid amount of 2.8-3.2l six cylinders and the smallest thing we use are T3/T4 hybrids with .82 turbine housings (or similar GT series turbos) but mostly full T4 with .58 turbine housings at smallest. WIth the larger T4 exhaust wheels they are similar to the T3 .82 in spool and total flow. The race cars usually use a T4 .96 or 1.06 hotside but you aren't making jam till 5500 and revving it out to 8k+ which is hard on the motors.
That's exactly the sort of knowledge I was looking for. It's a race only piece. I'm 5.3 liters in a V12 the pieces are the most bullet proof I've seen. Heron Head Hemi piston 7.8-1 compression. 
2 valves per cylinder. Great flow good swirl. I know I can go bigger but with a stone stock junkyard motor I'd be dreaming. It would be fine on the Dyno but do embarrassing things over 1/2 hour race.
Thank you sincerely
There's another factor to consider: vehicle weight. "In general", the heavier the car, the faster you want spool-up because it's needed to get the thing moving. It's why most pedestrian OEM turbo cars give the fleeting feeling of "Oh may, this thing's going to fly...", then runs out of steam.
The opposite is true as well. If you have a very light car, you want the turbos to spool up slower, since the engine may already be capable of spinning the tires at low speed; having double the power there is pointless. Far better to have it start adding in gradually above that - and be sure to have it pointed away from mere mortals!
My Midlana build is in the second category, using a T4 GTX3576R on a Honda 2.4 liter engine.
yupididit said:In reply to frenchyd :
Here you go Frenchy T3T4 T04E .63 A/R $108 each.
That would be a good choice for twins if your redline is low 6k range on a 5.3.
In reply to Paul_VR6 (Forum Supporter) :
Which is what he realistically needs. And in his price range. He says he'll wind the engine out to 7k rpm but we'll see.
I'm pretty decent at sizing turbos and if I was going to tt my v12 xjs that's what I would go for if I wanted super cheap turbos.
yupididit said:In reply to frenchyd :
Here you go Frenchy T3T4 T04E .63 A/R $108 each.
That's exactly the ones I selected before I got cold feet. (Thanks Paul for helping me).
Except EBay will sell me two with free shipping for $196.00 $20 bucks is $20 bucks more to spend on go faster stuff.
frenchyd said:yupididit said:In reply to frenchyd :
Here you go Frenchy T3T4 T04E .63 A/R $108 each.
That's exactly the ones I selected before I got cold feet. (Thanks Paul for helping me).
Except EBay will sell me two with free shipping for $196.00 $20 bucks is $20 bucks more to spend on go faster stuff.
Buy them now.
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