RS_Matt

It's not tosh at all, a moderately modded WRX is just about at it's max at 360/350 and at those power levels an STI would need serious money throwing at it to match the WRX's pace.

RS_Matt

Serious weight reduction, is yours the lightest Impreza you know of? Did you have a lot more than 690bhp when you ran the 8.83?

mickywrx

iTrader: (29)

It is tosh though, Matt. To get a newage WRX to 360/350 needs quite a big outlay. Moderately modified isn't over 100hp over standard, IMO.

It needs turbo, injectors, up-pipe decat, possibly intercooler and remap. TD04 is maxed at 300 ish, on a good day.

Newage STI, swap the turbo and remap. Add some injectors for a bit of safety maybe, but, STI pinks are something like 565cc anyway, opposed to the 440's of the WRX.

Who needs big injectors though, 380cc's FTW.

De-spec your car, and see how far away you are from me.

mickywrx

iTrader: (29)

Mikee's really good at this drag racing lark, really nice bloke as well.

RS_Matt

Trust me it costs peanuts to get both cars to 360bhp, my 360 capable turbo and injectors cost me £155!, at 360bhp the WRX has a huge advantage. An STI will need well over 400bhp to leave a WRX from the lights.

fat-thomas

iTrader: (4)

Is he still banging on about the wrx....what a case of sti envy.
12.8 at 260 bhp in my sti......can't ignore the facts!

jura11

iTrader: (7)

Hi there

As above pointed 2pot about the torque converter and their stall speeds,usually most of guys upgrading their Torque converter to higher stall

4EAT is not bad box when is properly build,but you will spend crazy money to get build to spec which will be reliable and price wise,anything from £1500 to £10k for Tony Rigoli box

Really depends on more factors

Thanks,Jura

Yes in standard form they will not last for long,but friend over in US running his standard box at 400whp and still on standard torque converter and car is used as drag car

But all depends on how you drive and how far you want to go,4EAT in standard form should be OK for about the 350-380bhp,beyond that,hard to say,I would say,you are risking as with every box

Thanks,Jura

RS_Matt

Serious and maybe game changing question.

Jura I'm of the understanding torque will probably kill my box and rods when going past 350lbft on a Newage WRX. If I stayed away from driving that will superheat my intercooler and engine/oil such as b-road blasts or trackdays what kind of relatively safe horsepower will my engine be happy at for day to day driving with the odd drag run?

Could I pull off 400/330 on a SC42/SC46 running low & efficiently cooler boost?

boosted

I have had experience in using and modifying auto boxes for drag racing, both successfully and not so successfully!
A lot of power lost through heating up ATF, why else do you need a chuffing big oil cooler!

fat-thomas

iTrader: (4)

not with your poverty spec bottom end and gearbox, you would need sti stuff to run that bhp

jura11

iTrader: (7)

Hi Matt

Yes torque usually kills the boxes or rods,have look we are running on EP3 turbo,we are making 382bhp at 15psi(1.0bar),but our torque is miserable 300lb-ft,why so low,because OE rods will snap beyond 300-320lbft,box should be OK for around 500-600bhp,but at this level I wouldn't run stock engine,although our friend running 705bhp on his stock K20

There is lots of but and if,but yes you should be OK if you will be running bellow 350lbft and running larger turbo with reasonable boost level

I know few people who run on their WRX 400bhp for several years without the issues and they're done several track days or drag runs,its really depends on more factors

Hope this help

Thanks,Jura

Yes agree usually what killing the autobox is heat,we are run too upgraded oil cooler on our 4EAT and we are run good oil at least,but usually what is weak on most of the 4EAT is valve body,most of them switching to manual valve body

How to say,if I would go again with 4EAT,probably I would remove this box and I would go with Powerglide box,they're probably best autoboxes and they're can be bought for really cheap,but modifying the box to Impreza can be very expensive

Thanks,Jura

Hi Dan

I wouldn't be so pessimistic on this,he should be OK if he will be careful and he will changing the oil etc

Thanks,Jura

boosted

Jura, my point being that making heat is not making the car go forwards, it's wasted energy, something an auto box is good at with no direct link between engine and gearbox.
Slow gear changes can destroy clutch packs, sharpen the change and increase clamp pressures and then the car becomes horrible to drive slowly, couple that to I high stall converter and you have a very uncomfortable car to drive on the road.

2pot

iTrader: (3)

What IS your point?:
You'd rather have a manual for strip?
You'd rather have a manual for street/strip?

RS_Matt

Jura, you're going to cost me a lot of money!

The more I read about what causes failures and what levels, I can definitely see that there could be away around it.

I'm starting to think with my conservative driving that heat build up (which I've also read claims gearboxes) and torque can be totally taken out of the equation.

My only question now is what bhp will the pistons be happy with? would 440/340 be too much for the odd track blast or single wot public road pull in 1st, 2nd or 3rd gear? (I've read 4th onwards are the main danger gears and I avoid using full throttle in those even now)

boosted

Manual for steer/strip. Never had a dedicated drag car, perhaps that will come eventually once I win the lottery and my children leave school

2pot

iTrader: (3)

Street/strip auto (assuming auto valve body): Don't over-do the line pressures. And mapping wise - for longevity of the clutch packs, reduce torque before the shift point.

boosted

This was on a 4.0 V8 turbo, not a wee impreza engine

2pot

iTrader: (3)

Applies to my 6 litre small block Plymouth with 727 torqueflight, or any street/strip auto.

boosted

Quite, we never went down the 16v V8 pushrod route. Choose an all aluminium 32v 1uzfe to turbo. Reliability has been good this season, but the auto box has brought some issues. So we have ditched the auto box and are now going full manual for next season. Cheaper and hopefully more reliable with the 600+hp

RS_Matt

Are Newage STI driveshafts longer than WRX ones? Especially 05> STIs?

jura11

iTrader: (7)

Hi Matt

Yes New age STI driveshafts are different,they're using different diff and due this you can't fit 6speed driveshaft on the WRX

But we are run WRX driveshafts without the issue at drag strip at various bhp levels and with NOS too and we are never broken or snapped driveshaft on the drag strip or track days

You shouldn't be worried about the driveshafts,they're cheap to replace,one driveshaft cost around £25-£50 and STI cost bit more there

Hope this help

Thanks,Jura

RS_Matt

I just meant will longer driveshafts incur higher transmission losses as I expect they will.

I'm just trying to piece together why the STI is so much slower than a WRX.

boosted

Driveshafts do not use power at all.
CV joints at an angle however will... Read into that what you want.

RS_Matt

I can imagine they will to an extent and more so as length is increased. It won't be anything to compare to the box though. Box might lose STI 20bhp over the WRX and the longer driveshafts 0.1-0.5bhp?

boosted

How can a shaft consume power?
The CV joints moving through an angle have friction to deal with and will consume energy. Longer shafts means less of an angle, so less energy consumption. The biggest factor would be the suspension and how low the car is (or how straight the shaft is) when it squats off the line.

RS_Matt

Rotational mass.

boosted

Neglegable considering the speed, weight and diameter. Ie slow, light and tiny.

Maz

iTrader: (34)

Rotational mass will affect the moment of inertia but to consider the shaft on it's own is a folly. The wheel/tyre mass, wheel/tyre width, brake disk mass will all affect the moment of inertia to a greater extent.
Furthermore if I'm not mistaken the STI shafts are actually lighter than the WRX. Thus irrespective of length they reduce the moment of inertia. Therefore reducing drivetrain losses.

RS_Matt

I know it's slight but I'm looking at accumulative factors. Why are they lighter? Stronger (but lighter) material for strength or to reduce already heavy drivetrain losses?

The Pink Ninja

iTrader: (23)

You know everything about why the WRX is a better, faster, stronger car yet you still asking the obvious questions, Do the maths on the numbers then try and work it out...obviously in private,
Its not all about 400m runs, Chuck some corners in and its a different ball game, but then you cant be that naive to think to think otherwise can you?