Bolt ons for St 20v

[forcexx]

Thinking of going turbo on my silvertop. How much would standard bottom end handle? Would like to run about 10-12 psi

Recommend computers that can be tuned well

And does anyone know if turbo manifolds can be sourced?
Easy to keep quads for turbo or easier to convert to single tb and would an xf tb be sufficient?

[jakel]

I think some people have gone like 11psi on stock silvertop.

[Skylar]

There is (was?) a second hand rex kelway 16/20v manifold in Parts for sale here a week or so ago in Tas. If that's not there, then get a rex kelway manifold off AJPS.

I think they'll handle that much boost if you decompress them, or water/meth injection. On standard comp of 10.5:1, I would only run a weeny bit of boost on pump fuel.

Keeping the quads depends on whether you can get an airbox made and mostly on whether your tuner is up to the task of tuning a turbo car with ITB's. XF tb would be plenty. You sound so oldschool saying XF tb, I haven't heard of anyone use one of those in years!

Adaptronic E420D or E440 select, Vipec V44, Link G4 atom and storm, Haltech sport 1000 will handle the job fine (4d tuning avail).

[slydar]

4age's are a short rod ratio engine. which means theyre not really prone to knock. if tuned properly 10psi i safe. plenty have done it before.

[forcexx]

I owned Gemini before this and built a high performance na motor and xf throttle was the tb of choice. A mate of mine has a 16v 4age ke70 with one on it also and it was running 13 sec quarters. Can prob get a box made up but wouldn't know where to measure for it or whatever. If you get a decent tune you should be able to run standard comp on about 8psi yeah? Meth injection is too much mucking around for a track/streeter. So would it just be worth getting a set of forgies? And refresh the bottom end while I'm at it or seeing as I will be doing timing belt and water pump get a thicker gasket and drop comp to 9:1 or something?

[Skylar]

Yeah, everyone used XF tb's back in the day. I rarely hear of it these days.

I changed my mind. Run some boost through the thing. VVT will reduce dynamic compression ratio. and although I have no tuning experience with a 20v, the 16v takes a lot to make it detonate.

If you can fork up the $$$ for forgies, why not... but I like testing things and see what you can do with stock stuff. So, if it were me, I'd leave stock pistons in it and have a spare short motor with forgies in case the motor fails or you want to really wind up the boost.

Oh, and try to get a "good" tune rather than a "decent" one. They'll probably last the same amount of time but a good tune will be nicer to drive and make power for longer through the rev range.

[Skylar]

http://img824.imageshack.us/img824/6097/20valvesilvertopthrottl.jpg
Measure that and cut a plate cut that bolts on. Put some sides and a roof on it but make sure it's removable from the floor so you can bolt the floor to the tb's then the rest to the floor.

[Vance]

will handle 6-8psi properly. with any engine you can retard the timing to reduce the static compression ratio so you can handle more boost you you wont be getting much more power out of it and it will feel kinda lazy. youre better off putting lower compression pistons in if you want to handle more boost. the stock bottom end bar the high comp pistons will handle 15psi and more easily

[forcexx]

so you dont recommend just throwing a thick copper gasket on it and going for the higher boost? with the vvt lowering the static compression will it seem more laggy or?

[lolwat]

if your going to be ripping the head off, do a set of lower comp pistons and shit

[Skylar]

will handle 6-8psi properly. with any engine you can retard the timing to reduce the static compression ratio so you can handle more boost you you wont be getting much more power out of it and it will feel kinda lazy. youre better off putting lower compression pistons in if you want to handle more boost. the stock bottom end bar the high comp pistons will handle 15psi and more easily

SCR is a ratio of combustion chamber + head gasket + swept volumes:combustion chamber + head gasket volumes. Retarding timing doesn't change SCR or DCR.

DCR brings the valves closing into play and reduces swept volume in the above equation. with the VVT, you can close the valve 70deg after BDC.

I think what rio meant to say was, the amount of timing you can will depend on boost. You can boost the engine up to X psi without pulling too much timing(normal timing retard due to increased combustion chamber charge density) but after that, you need to pull a lot of timing and the engine won't really make much more power with more boost even if the turbo is still producing air at a decent temperature. Where the X psi is, I don't know. BUT up to X psi, it will take it fine and make good power.

Lowering SCR through a thicker head gasket will make the car a little more laggy than stock hg. Like I said before VVT has no influence on SCR. Thick head gaskets reduce the amount of quench which is probably a bad thing but engines do funny things. ie All I can say is, a head gasket will make it more laggy, whether it reduces the knock threshold and slows flame front propagation speed(makes less power), I don't know and can't tell you.

[SHEPPO3930]

plenty of people have turbo'd the ST 20v with great results. figures i've seen quoted have been over 160rwkw with 0.7-0.8bar boost, and 140rwkw with only 0.4-0.5bar.

you'd want to keep the standard HG thickness to retain the squish band the ST head has, as that will be better for reducing detonation rather than reducing the comp with a thicker HG and loosing the squish.

i'm in the process of building up a ST 20v turbo for my TA22 celica, and i'll be going high comp & low boost.

[Matt]

Hit a guy actiondan or bazda up for custom inlet manifolds. Search for them on facebook or the net and you'll find em. NZ based

Awesome work, and can be made for both FWD and RWD. The turbo manifolds are pretty good too, loads of exp. with turboing 4ages, and they regularly get 200kw atw on around 18psi.

[DX20VT]

Standard 20V's will handle boost well, have seen one here at 18psi on standard compression, but it was done by a really good tuner. just cant run too much advance.
Otherwsie the rest is fine.

I run a s/h ST 20V with a set of s/h 4agze pistons and new rings on 20psi in a race car for two years before I sold it as a running engine.
It is all in the tune.

[forcexx]

Sorry what is s/h? And does not being able to run alot of advance deprive the power or just won't make it's potential but still makes decent power? Also I can't seem to find the actiondan or bazda, any more info?

[DX20VT]

sorry, s/h refers to secondhand.

[forcexx]

oh haha, yeah cheers. first thing i will be doing is chucking it in n/a with new timing belt and thinking of getting a davis craig water pump or whatever, opinions? then i will start getting the turbo stuff together

[SHEPPO3930]

Side note,

A member on here (Sheldrake) was running 82mm 4AGZE Aries forged pistons in a ST 20v, with 19psi made over 200kw at the wheels (236kw to be exact, but the dyno in question is a little happy). The comp ratio was worked out to be 9.97:1 (I cc'd the pistons and chamber) with a TRD head gasket.

Another example is a bloke (video on ebay) running a Rotrex supercharger on a stock internal ST 20v, made over 200kw at the wheels with 14psi. When he raised the boost (and revs), is when the motor broke, and all that happened was the ring lands on the pistons broke. He's now replaced the pistons with 8.9:1 GZE pistons with flycuts to suit the 20v head. Engine went on to make the same power on the same boost level with the lower comp slugs.

Bottom line, the ST 20v likes boost. Either in stock form, or with GZE slugs fitted.