Austarion

My engine has just been rebuilt, apparently has high compression pistons, has a ported head, 2.5 exhaust and I am planning to intercool when doing the MPI with computer.... Do you think it is worth me bothering with a custom plunum?

oped wrote:......apparently has high compression pistons.....

How far do you intend going with your motor, 200hp, 300hp, beyond that???

If your only going for about 200hp at the wheels the standard L300 plenum will be fine, Ive seen 2 cars run this in person and it works well. If you want more your better off spending the extra money now and putting on a bigger plenum L300 runners. Otherwise if you decide you want a bigger plenum later on its more money and more trouble.

My goal would probably be 300hp at the moment. Lets say I had a L300 ready to stick on... How much extra would a custom plenum probably be?
And with the custom plenum, can it be made so that the intercooler piping goes around the engine like the sonata one?

Plenum would depend on if its a custom alloy one or a generic aftermarket one. If you know someone in the metal business they should be able to knock you up a basic one.

In Melbourne you have 2 Starion workshops that could lead you in the right direction.
There is Chris from www.beyondthelimit.com.au
or you have Flav who is on the forums. Either of these guys can help you out.

Plenums usualy place the throttle body at the front facing towards the front of the car. This helps with neater intercooler piping. If someone were to make a totally custom one you could get the throttle body placed wherever you wanted.

If I can add my opinion, if you dont want sequential injection and multi-coil at the start you wont need a L300 dizzy, you can use the starion one but just have to lock the mechanical advance. Another option is you can use a sonata dizzy and then swap in disc inside when you decide to go the multicoil and sequential injection option.

Having used both the sonata manifold and the l300 one (but modified) i would agree with going the L300 from the start. The reason being the ease of having the thermostat housing facing the right way and secondly you can get a custom plenum to be welded on the L300 manifold and have the benefits of a foward facing throttle body and a thermostat thats at the front of the manifold.

In the end though its a case of how far you want to go and how much power you can afford to make. Given that you dont even know whats in your rebuilt engine, your goal of 300hp is still a way to go.

"high compression pistons" is a relative term. Relative to the SOHC Starion motor, 8.0:1 could mean "high compression pistons". Either way, an intercooler is a must, but you don't encessarily have to fit one when you go MPI, but it is recommended that you do it when you change the ECU and inlet manifold. Modifying the piperwork later on if and when you change the plenum and throttle body isn't a major drama.

there is more work in the sonata one than the l300. the colant system has to reworked if you want the engine to have proper cooling. this requires the rear coolant outlet to have a blank welded inplace with a 4 mm hole in the middle. and the foward coolant outlet must be machined in and a pipe welded on that returns to the thermostat housing.

anything over 350 rwhp i would suggest a custom inlet manifold.
i'm about halfway through making a stainless steel similar to the VW on
www.hypertune.net

at present i'm getting my runners from 75mm billet stainless bar on a cnc lathe at work.

SORRY FOR THREAD HYJACK

if it works well i can can duplicate this manifold as i have a milling machine and a TIG welder at home. But due to the man hours involved in machining stainless and welding + the cost of materials they won't be cheap. The runners anlone have cost me $1100 dollars. they will only available in stainless as i don't have an AC high freqeuncy tig to do ally.

On the flip side my sonata manifold will most likly be for sale towards the end of the year.

here are some pics

it will come with AU falcon 70mm throttle, fuel rail, 4 x serviced 550 cc rx7 injectors and a malpassi reg and custom thermostat housing cover. but like i said won't be for six months yet.

Ok igottasicjb.
I'm just wondering why do you think that the cooling on the sonata manifold needs to be modified. I'm in the middle of changing over my L300 manifold to a sonata one so i can get a better set up for intercooler piping. I wondered about the different thermostat outlet locations but when i looked at the coolant flow path as shown on the engine diagram it appeared that there wasn't an exact path shown and that it just kinda flowed from the lower half of the block to the top through all the coolant passages in the head pretty evenly. I may be incorrect by that as i have no idea as to what path the coolant flow has.

Also the flow of the water through the block is exactly the same with the L300 and the Sonata when the thermostat is closed. The heater line is still in the same place and it flows from there to the water pump and then through the engine so i couldn't see a difference when the thermostat is closed.
And the thermostat lets off heated water and then cools it so it doesn't really seem as though the changing of the water coolant path lines is really a neccessity.
I have both manifolds at the moment and i'm at the moment changing from the L300 to the Sonata to get a shorter layout for the intercooler piping. I haven't heard about anyone having any problems with cooling so i figured it'd be fine.

By the way how much work was needed to get that manifold looking so sweetly polished.

Also for anyone trying to find a sonata manifold and the sonata dizzy with the TDC marking for sequential ignition. It was just the manifold with no throttle body but everything else was there.
I got my manifold and dizzy for $150 total from the hyundai wreckers in Brendale on the northside of Brisbane. Don't know why but all those prices makes it seem like you guys are getting jipped.

I looked at the price associated with getting a custom plenum for the L300 manifold and got the sonata manifold to wait till i get keen to go for big numbers once everything else is sorted.