41 replies to this topic

[Nev]

Is there a replacement mod for our narrow TBs ????

[MEAGY]

Same reason we have small turbos as standard.....cause vaux wanted a 200bhp engine & thats what they got! If they want to produce a `racier` engine they would be skint and there would be twice as many dead vxts around lol You have to bore out your inlet and retap the holes for alarger TB whivh might/might not fit & would really weaken the inlet!

[slindborg]

friend of mine made this for his C20LET


here are some build pics there are 4 main parts to the manifold.

first is a head flange this is cnc cut on a milling machine, out of billet alloy




in this pic you can also see one of the runners that is the 2nd main part to the manifold

next is the base plate for the plenum


the ''lines'' are just machining marks that look worse because of the camera, you cannot feel them to touch.

this plate has built in velocity stacks for proper air flow.

and the final part is the plenum.

add all these bits together and you have


cannot wait to get it fitted now and get it back on the Rolling road to see how it effects the power output

some pics of it all fitted up (with one bolt lol)



uses a Cavalier V6 throttle body, EVO plenum and the rest is CNC

[Nev]

Ahha, so he used a Cavalier V6 throttlebody. I wonder if the electrical signals sent by my Z20LET TB will be the same as, say the VXR Vectra TB ? If they were, then presumably you could do a like for like switch (but obviously have to make considerable fitting mods).

Edited by Nev, 31 December 2008 - 09:42 AM.

[cheeky_chops]

Ahha, so he used a Cavalier V6 throttlebody.

That was a different engine (c20LET) and would guess it isnt fly by wire for starters...

There is a guy on asta sport forum having a inlet manifuld made up by nortech i believe, £600. However, on its own, you main problem is still going to be a bottleneck of pressure at the exhaust manifold....

[Nev]

Cheeky, are you saying you thing the entire exhaust manifold is a major restriction? I have looked at it and it is certainly very cramped with poor angles, I have considered getting one made up when I get the 3" exhaust done, possibly with a brand new 350+ BHP turbo.

[slindborg]

Ahha, so he used a Cavalier V6 throttlebody.

That was a different engine (c20LET) and would guess it isnt fly by wire for starters...

There is a guy on asta sport forum having a inlet manifuld made up by nortech i believe, £600. However, on its own, you main problem is still going to be a bottleneck of pressure at the exhaust manifold....

correct, but if you fit a suitable ETB then wayhey


the std cast exhaust manifold is an epic problem, usually for cylinder 3 when you get things cranked up high

[cnrandall]

If you want 350bhp there is no need to change the throttle body. What you will need to do however is change the Turbo, probably something like a GT28rs and then get a decent chargecooler and exhaust on there and, of course, get it mapped accordingly. Trouble with all of that is I'm not sure how happy the standard pistons would be with any sustained running so you're into opening up the engine.

[slindborg]

aslong as the std Z20LET pistons are Forged Mahle items (as the C20LET was) then they are good for 350bhp all day long (well as all day long on max chat as any engine likes lol)

[cnrandall]

aslong as the std Z20LET pistons are Forged Mahle items (as the C20LET was) then they are good for 350bhp all day long (well as all day long on max chat as any engine likes lol)

The ZLET pistons aren't the forged Mahle ones though. On the Z20LEH they are but on the LET they are cast items.

[cheeky_chops]

the std cast exhaust manifold is an epic problem, usually for cylinder 3 when you get things cranked up high

Read a couple of people having the piston in cylinder 3 evaporate - the regal/Dbilas exhaust mani will remove some of the restriction and keep OEM dimensions

Just to add, i freed up my inlet side alot and when i went back to courts for a new remap, the boost was "bouncing" between 18/12psi. Jon applied a specific map as he said the VXR220 turbos turbine/compressor wheels dont seem as well chosen as the astra VXR turbo and leads to a pressure buildup in the zorst manifold as the turbine cant gobble up enough gasses! This, causing the actuator to pop open/closed, hence the bouncing boost

[cnrandall]

the std cast exhaust manifold is an epic problem, usually for cylinder 3 when you get things cranked up high

Read a couple of people having the piston in cylinder 3 evaporate - the regal/Dbilas exhaust mani will remove some of the restriction and keep OEM dimensions

Just to add, i freed up my inlet side alot and when i went back to courts for a new remap, the boost was "bouncing" between 18/12psi. Jon applied a specific map as he said the VXR220 turbos turbine/compressor wheels dont seem as well chosen as the astra VXR turbo and leads to a pressure buildup in the zorst manifold as the turbine cant gobble up enough gasses! This, causing the actuator to pop open/closed, hence the bouncing boost

That's likely an issue with too much boost causing the turbo to overspeed. With the tiny inlet to the turbine and small A/R that's always going to be a very easy thing to do. The other trouble the k_04 turbo seems to have under high boost is weak thrust bearings. TBO, if you are running the standard turbo it's wise to keep boost to safe levels.

Th Dbilas manifold has a bigger inlet and I think a larger A/R than the stock manifold so isn't a bad upgrade. That said, if you want to get into another turbo it would be more sensible to get a garret turbo and do the job properly.

[slindborg]

the std cast exhaust manifold is an epic problem, usually for cylinder 3 when you get things cranked up high

Read a couple of people having the piston in cylinder 3 evaporate - the regal/Dbilas exhaust mani will remove some of the restriction and keep OEM dimensions

Just to add, i freed up my inlet side alot and when i went back to courts for a new remap, the boost was "bouncing" between 18/12psi. Jon applied a specific map as he said the VXR220 turbos turbine/compressor wheels dont seem as well chosen as the astra VXR turbo and leads to a pressure buildup in the zorst manifold as the turbine cant gobble up enough gasses! This, causing the actuator to pop open/closed, hence the bouncing boost

That's likely an issue with too much boost causing the turbo to overspeed. With the tiny inlet to the turbine and small A/R that's always going to be a very easy thing to do. The other trouble the k_04 turbo seems to have under high boost is weak thrust bearings. TBO, if you are running the standard turbo it's wise to keep boost to safe levels.

Th Dbilas manifold has a bigger inlet and I think a larger A/R than the stock manifold so isn't a bad upgrade. That said, if you want to get into another turbo it would be more sensible to get a garret turbo and do the job properly.

indeed, screw the KKK and all its massive heat generation/p*ss poor manifold setup.

[drew]

what size is the throttle flap. m8.

[NickB787]

Can I revive this

I am after a larger TB than 56mm which works on the z20let loom any ideas? It's for mt ecu conversion

I have found that someone as running a 60mm tb by Jenvey on a z20let vx220 so FBW, anyone had any dealings? they make larger ones 70 should be fine

Jenvey

Edited by NickB777, 05 November 2010 - 07:19 PM.

[NickB787]

Just found out it was cable operated they do one for the EVO FBW will call them

[Exmantaa]

Can I revive this

I am after a larger TB than 56mm which works on the z20let loom any ideas? It's for mt ecu conversion

I have found that someone as running a 60mm tb by Jenvey on a z20let vx220 so FBW, anyone had any dealings? they make larger ones 70 should be fine

Jenvey

That's for the "Supercharged LET ecu conversion?
Always thought that this could run with the 68mm SC TB, but if not that's one more reason to continue the US LSJ ecu route...

[NickB787]

Can I revive this

I am after a larger TB than 56mm which works on the z20let loom any ideas? It's for mt ecu conversion

I have found that someone as running a 60mm tb by Jenvey on a z20let vx220 so FBW, anyone had any dealings? they make larger ones 70 should be fine

Jenvey

That's for the "Supercharged LET ecu conversion?
Always thought that this could run with the 68mm SC TB, but if not that's one more reason to continue the US LSJ ecu route...

I gather the z20let loom plug set up is different, I know what you mean I have a DTA sat here and I keep looking at it....

found a couple of 56mm TB which are bored out to 63mm

Edited by NickB777, 05 November 2010 - 08:25 PM.

[The Batman]

Got a 56mm z20 tb in the garage, if you found a 60mm butterfly valve then you could probably port it all and fit that... But still 8mm down... Which isnt the way to go Ideally a nice 70mm will do if it is not cable driven. Why cant the normal tb be fitted? Just doesn't work with the z20 wiring?

[Winstar]

must have missed this first time round the answer to the original question is that once your post turbo then the velocity doesn't change much just the gas density which isn't as much of a pressure loss. As for the SC aplication then as the TB is pre-charger then the size of the TB will be a real restriction, what does klasen run on his 600 bhp speedster?