21 Turbo High comp R21T engine?

[|sAs|]

Hi.
Has anyone built a high compression engine for a 21T?

My goal is just over 200-225bhp and low lag. The engine is completely in bits so now would be a good time to change things around. An engine builder I spoke to recommended to build it as an NA but keeping the turbo cam and valves.
The main purpose with the car is to go to car meets and the occasional street run. It is a pure hobby vehicle so no extreme demands.
I'm thinking going for a set of TXI pistons/sleeves/rods. Would it work? Would I need the crankshaft as well?
I'm also thinking a quite small but modern turbo.

Ideas? Feel free to bash my ideas if there are completely insane, but the main point I'd like to make is that I want a 21TQ with around 200-225 bhp and really low lag.

 

[Haz]

Not that I'm aware of.
Apparently the basic rule is .1 comp = 1* in = 1psi.
Raising compression from 8:1 to 9:1 would reduce boost from a safe 16psi to 6psi and the 21 engine doesn't like ign.
A similar sized modern turbo will reduce lag just with a turbo swap on an oe engine. Replacing both the top mount cooler and turbo elbow restrictions will allow for more flow.
The turbo cam is no good for na applications, well, it's a mild cam really and runs out of puff about 5400 revs but an n.a. cam will move the powerband up thus making more bhp.
Txi bits are rare and could be a costly route. Unsure how the blocks differ. It's a 12v head so the cam won't work.
Iirc an an oe engine can be mapped to 240bhp, with standalone and injectors? Bearing in mind the Quadra system saps a lot of power.

 

[DaveL485]

I tried it, it blew the head gasket fire ring out into the water jacket when I stuck some decent boost through it.

I'd imagine a standard engine with a GTX2860 would be pretty responsive.

 

[|sAs|]

Not that I'm aware of.
Apparently the basic rule is .1 comp = 1* in = 1psi.
Raising compression from 8:1 to 9:1 would reduce boost from a safe 16psi to 6psi and the 21 engine doesn't like ign.
A similar sized modern turbo will reduce lag just with a turbo swap on an oe engine. Replacing both the top mount cooler and turbo elbow restrictions will allow for more flow.
The turbo cam is no good for na applications, well, it's a mild cam really and runs out of puff about 5400 revs but an n.a. cam will move the powerband up thus making more bhp.
Txi bits are rare and could be a costly route. Unsure how the blocks differ. It's a 12v head so the cam won't work.
Iirc an an oe engine can be mapped to 240bhp, with standalone and injectors? Bearing in mind the Quadra system saps a lot of power.

I was going to use the turbo bits and only change the pistons and whatever parts necessary to go with those and go low boost with a smaller turbo.
Front mount is on the list as well.. Was thinking something like this in front of the rad: Intercooler 460x300x85 - 2,5'
Should go in with minor mods to the front mask.

I tried it, it blew the head gasket fire ring out into the water jacket when I stuck some decent boost through it.

I'd imagine a standard engine with a GTX2860 would be pretty responsive.

You tried TXI pistons in an otherwise stock turbo engine?

It sounds like a better route would go with stock internals and optimise flow in the exhaust manifold and pressure piping together with a better turbo?

 

[DaveL485]

You tried TXI pistons in an otherwise stock turbo engine?

No, I had a head that was over-skimmed, so I had a bit more taken off it to try high comp.

 

[la21t]

Mine with a GTX2860 fitted.

Its got a very lumpy cam and low comp pistons but you can see that it starts to come on boost rather quickly.

As Dave has said, it'd be quite a nice drive on a standard engine.

I've often said it but when I left Scoff with Adaptronic on standard engine and a T34, the car was at its most tractable. I have no regrets about what I've done as its phenomenal fun but if I ever owned a stock daily, I'd get an ECU on it and a modern turbo and have a marvellous mile muncher.

 

[Deleted member 486]

What do you mean by "low lag"? Do you mean a fast time-to-torque (i.e. minimal delay between planting the throttle and getting full boost) or a low boost threshold (i.e. peak torque at a low rpm)?

Both of them will be helped by a lower inertia turbo (don't confuse this with smaller as a larger turbo can have a lower inertia than a smaller one if design is better). A smaller turbo will help with faster spool up due to it having a smaller diameter turbine inlet but this will choke the system at higher revs.
A twin scroll manifold and turbo will help even further and is probably the route you should be looking to go down if time-to-torque is your key motivator. A larger twin scroll can give you improved time-to-torque compared to a smaller single-scroll and will help to reduce the back-pressure of a smaller turbo at higher engine speeds.

Increased c/r is only really done for efficiency. It won't really help with turbo response BUT it will increase the N/A torque of the engine which will mask some of the lag.

The biggest problem you will have if you want peak torque low down is the fact that the 21T lump is a single cam with no variable valve timing. Modern engines use the VVT systems to give a lot of overlap at low engine speeds to scavenge and "blow-through" which massively increases low-end end torque. If you set-up the cam to give you that then you'll have pretty horrific exhaust temperatures at high speed as well as the risk of in-turbine combustion and so you'll struggle to get power.

Personally, I would probably leave the bottom end of the engine alone. Go for a twin scroll turbo with an equal length manifold and shorten / reduce the volume of the path from the compressor to the throttle body. Also, try to make the air path in to the compressor as smooth as possible - this makes a huge difference to the compressor efficiencies.



If you want to go really silly then just pinch an e-booster & one-way valve from a Merc E53 AMG, try to get a 48V battery somewhere and run a DCC converter then get an ECU that can control it. That will really make a monster difference to low-end torque and lag!

 

[21 quadra]

, the bottom of the

TXI engine piston rings are more narrow than J7R 756, ) are from the top 1.6mm, 1.8mm and oil ring 3mm, for quadra the rings are 1.8mm, 2mm, 4mm, con rod are same and piston sleeves are same, 5mm longer sleeves are from 2165 cc J7T 754 and 755,,in that sleeves the difference 5mm longer are from bottom rubber sealing to top, i make that in my quadra cutting the top of that sleeves ( J7T 756 ) using con rods from TXI, also the dom of the TXI pistons is difference.

You can use TXI block and TXI heads to have a 12 valve turbo engine, using and TXI crankshaft because is same to j7r 756 and keeping flywhell of j7r 756 and also the ECU of J7R 756 with programm and mabe new bigger ingectors according size of turbo, header and exhaust, also TXI throttle are 2mm bigger, you can by piston rings from Mahle asking for piston Dia 88, rings 1.8mm / 2mm / 4mm is to chip, 60€ all set, if you asking rings for J7R 756 is more - more = more expensive.
Oil pump original Kolbensmith new i was by from greek internet shop for only 50 euros.

If you need any more info i am here to help as i can

 

[21 quadra]

Compretion of engine J7R 752 non cat are 8:1, in quadra cat J7R 756 are 8.5:1