scottspeed

pipe sizes make a huge difference ESPECIALLY off boost or as it transitions into boost. Think of it as an NA engine which you can change the powerband through header sizes and lengths,

I havent done any of these uppipes in a long time, thought no one wanted this stuff anymore? :-\ Im currently trying to move shop and catch up on work, but would be keen to do a run of some for my stock, probably be about 2months away though at the moment. From my testing, the lesser welds/joins in the exhaust pipes the better they go. As pappu asked, if you were going to the trouble of removing the flexpart, its just as easy to weld in a complete new pipe.

Heres a slightly tuned car on stock up pipe and new one piece custom 1.750" item and yes evowrx that was my website, but i took it offline as I have too much workload

The decent japanese branded large 2 inch up-pipes, actually have a choke (like a carburetor venturi) fitted inside out of view, to actually give the exhaust gas a speed up to lessen the lag associated with a plain 2 inch up-pipe

Your definitely thinking along the right lines, I see so many 2inch or big up pipes that make the cars a dog off boost to drive. Using 1.750" matches the ID of the OEM exhaust manifold so the speed of the exhaust gases don’t slow down (going into a bigger tube) or speed up and get restricted (going into a smaller tube). If you use the proper size tubing it also means we have proper sized ports. The OEM gasket is a very high quality gasket and its designed to sit back from the extreme temps of the exhaust. When you over-port your flanges the OEM gasket is now exposed to the extreme temps and will burn out very quick. I thought most people knew this trick of the up-pipe and wondered why so many people thought it was the twisting of the turbo made the power. Hence i thought i might join your site and see if i could help some of you guys with some proper technical info.

stock up pipe is the worst for flow. A one piece one, just about always ads 10kw, on the power range your after the stock turbo is maxed out, but this would help on spool up and add slightly to overall power.

intake mods do change the power band, and freeing up will normally increase power. Depends on what you class as freeing up the intake tract as. Changes to the runner lengths (std is too long for higher rpm power) and increases to the plenium volume will normally carry power higher up in the rpm. Better intake hose to turbo will also increase performance, and ever replacing the end tank on the top mount closest to the throttle body with a custom tapered item will increase power.

yes I think from memory the plug and play g4 should already be configured to run this sensor. If you really want it to read quicker like the bosch hot wire type, you can carefully whittle the plastic tip down with a sharp blade to reveal more of the resistor.

to plOx, most road cars are fine with only ACT because they are not tuned to the edge. But on a race car which may be .5deg ignition away from detonation or even 1 deg into detonation, a slight change in airbox temp can have a huge effect on the engine. When you have the time the factory does and resources, by using both sensors they end up with a more fuel efficient car with a constant power range over a wider range of temps. Older cars would always go good on a cold day/night whereas this isnt felt so much on newer cars.

hmmm, I'm Not going to get too much into this as I make a living tuning top level rally cars. A good tuner should be able to see how MAF sensor will show relative ambient/outside air temps being drawn into the intake system. and the one in the manifold will show how beaten up its gotten on the way in Simple example, one before turbo, one after turbo and cooler, which gives you a temperature drop range which allows you to enter ecu information to change ignition/fuel and boost requests. A car with 30deg manifold temp doesnt mean much when your tuning a race engine or performance engine if you cant reference it to outside airtemp. 30 deg manifold temp with a 25deg airflow sensor reading requires a different ignition/fuel/boost compensation valve compared to if it saw 5deg airflow temp reading.

If your looking for easy power, a one piece up pipe, 1.750" diameter will add 10kw over the stock item. Ever wondered why people say twisting the turbo made more power, most cases nothing to do with the twisting, its that the new up pipe fixes the factory restriction.

Yes this is the ACT (air charge temperature) and yes the AAT (ambient air temp) is taken from the airflow meter. Most people seem to not pay enough attention to keeping these in place. Big performance gains and constant power readings across a wide temperature range can be found if tuners utalise good compensation tables. Also most important to keeping a cast piston late model sti engine in surviving in one piece. As the factory cost cuts on engine components, reliablity is made better by smarter electronics.

1.6mm steel shim "listed subaru OEM gaskets" actually measure slightly under 1.5mm once torqued up. This would give 7.9:1(providing everything else is the sizes/volumes I used) without allowing for any head milling which would raise it slightly, so yeah be good choice.

If you decide to port them, make sure you stop about 2mm away from the gasket edge. These gaskets cant actually survive the exhaust temperatures that are generated, so need some shielding from direct heat (much the same as a headgasket is always larger in diameter than the bores). If you port to exactly the same size as the gaskets you will find gasket life is severely reduced.

ok if the gasket is listed as 1.6mm the compression would be 7.85:1, but from all the gaskets i have seen this is a subaru figure and a gasket that has been torqued down will normally come in under 1.5mm thick. At 1.5mm compression would be 7.9:1. Alot of factory engines arent actually the compression listed, and its not uncommon to find engines under 7.0:1 from factory. Even worse with aftermarket pistons or gaskets fitted. Unless you were wanting to measure cylinder head and piston bowl volumes, and piston crown heights and gasket thicknesses from your original engine it would be almost complete luck to achieve the identical compression. As an example most of the complete version 7 engines (that use this style of short block) list a compression of 8.0:1 but actually checking of engines have never shown any engine this high. Most range 7.85-7.95:1, hence blueprinting an engine can improve performance quite dramatically. I wouldnt be too concerned for a road car, a slightly lesser compression ratio would benefit slightly as less chance to knock on incorrect fuels. Japanese specification subaru turbo cars are actually ment to run 100octane fuel which is why certain non export models have had detonation issues when imported in NZ.

If your meaning you have rounded the heads off, Use a 12mm 6 point socket on an extension and hammer it onto the bolt head, If this still spins, go to an 11mm 12point socket, and failing this your gonna need to drill the heads off. They get done up to 35ft/lbs and the 8mm ones around the crankcase outter are 18ft/lbs

OK. pistons in these ver 7sti shortblocks have a 6cc dish, and are approx 1.5mm down from the top of the block, assuming your v3 heads have a stockish combustion volume of 46cc, then with the thick head gaskets (1.35mm) will give compression ratio of 8.0:1, and if you run the thin headgaskets (.6mm) then compression will be 8.54:1 So, probably wanna order stock thick head gaskets, preferable the sti steel shim ones. If your engine hasnt been overheated or apart before the stock bolts will be fine, or sta parts used to do some cheap stock type bolts. Or chat to a decent engine shop and you can probably buy some new unused factory bolts cheap. (I normally have a excess of stock new bolts that are left overs from subaru new engines built for customers) For about an extra $80 (or for the money you save on not buying new bolts) get both heads surfaced to make sure they are 100% flat Make sure you torque steel gaskets up, then back the bolts off, then retorque them all up. Dont run antifreeze in the engine for the 1st 100km of use and you should never have any gasket issues.

Yeah, I kinda get sick of hearing some of the bad information some of the so called self experts give you guys sometimes. Especially as i have factory inside info and been building and tuning subaru motorsport only stuff for over 12 years now. Bang for buck you cant go wrong with one of these blocks as a replacement or a start point for a rocket

The stock crank is VERY good quality and will easily out last some of these "aftermarket performance" chinese cranks. The cosworth item is nice but is also $500usd over priced! The biggest gain is not the strength or looks or oiling, as the factory also has no oiling issues (more too many wannabe engine builders dont understand what bearing clearances are needed for certain applications!) The biggest gain is the loss of reciprocating weight. On a circuit or competition car this can take seconds of times. It will never show any HP gain on a dyno, which is why people say they dont make any difference. Definately a lighter crank will show gains to a decent racecar in its laptimes, just not on a dyno run.

if it ver5 sti it has an open deck block. It does Have better heads and cams than the trusty Ver4 but the blocks distort the bores and the head gaskets give issues on the open deck block when you pump some boost. If you dont over rev it or go about 240kw the stock rods will just live, and if its tuned right with a set of head studs fitted it should be all happy. If your wanting something mega grunty and abusable go to a better shortblock option

This IS a V7 (bugeye) shortblock. yes these are the strong forged piston ones. V7 has a raised centre section of the piston bowl V8-9-10- have a circular dish and are cast. Only the sti 207 high output blocks are semiclosed deck. These cheap V7 shortblocks now have the superseeded parts from subaru in them, so normally have v8 onwards rods (tappered smallend) as well as the v8 non nitrided but crossdrilled main journal cranks. these specs do change depending how old the stock is. Talk from sti engineers is that when america was 1st launching the wrx bugeye cars, some head director specified the wrong STi engine code. This was to seriously effect the pricing so the order was changed to the correct basic wrx 205 opendeck, cast piston engines. Hence subaru ended up with a few ten thousand left over sti 207 engine assemblies, that they're still selling off cheap.