Granby

iTrader: (5)

Has anyone had good or bad results using aftermarket equal or unequal headers on there scooby, the reason i ask is that I've been advised against a certain make of equal length headers (which i won't name) as they a power loss, so anyones views would be appreciated.

Cheers
Granby

The Fixer

There are around seven different sets of headers on the market, they all perform very similar in terms of power / torque gains.

In terms of equal or unequal length there arent any true equal length ones on the market and the main difference is that the ones which are nearly equal lose a bit of the scooby / boxer rumble, the unequal variety keep this noise.

IMHO the best type to go for in terms of performance / noise / quality and value for money are the Gruppe-S style un equal length.

To get the best out them you will need to remap which ever type you go for.

Granby

iTrader: (5)

Thanks very much for the reply, just a couple of questions, do you think this is a worthwhile upgrade (MY04 WRX with decat uppipe - decat downpipe - Ninja backbox - remap by Bob Rawle) has been on a rolling road and got 269bhp / 300lbs and where can i get the Gruppe-S headers

Cheers
Granby

WRX_Rich

iTrader: (5)

mate all header did for me was extra torque - yeah i love them but so don't
i did it as I thought it was a nice way of doing away with the up pipe cat

you would have to get the car mapped again

think you would get more from injectors and turbo

Granby

iTrader: (5)

I was thinking that as well

The Fixer

Its about the overall set-up not just the individual componants, injectors will only be neccessary when you start to flow more air into the engine via induction kits, new turbos etc and the current injectors cant flow any more. If you are wanting 350 ish on the WRX get yourself a VF35 and intercooler off an STi followed by a remap

Welloilbeefhooked

iTrader: (3)

Do you really need a remap for headers? Why is this? I can see the remap being needed for intake mods but surely the exhaust is just exiting quicker.

On some of my older cars there was a distinct scavanging effect from the manifold/headers. I am pressuming that a turbo would cause a sufficient restriction to negate this effect?

The Fixer

Any modifications that allow an engine to "breathe" better either on the inlet or the exhaust side needs accounting for in terms of fuel & ignition, just one example by fitting headers is that the headers will more than likely move the spool up point of the turbo so fueling & ignition will need setting up to account for this.

Welloilbeefhooked

iTrader: (3)

Conrad,

So the spool up will be earlier than before due to better gas flow? I'm assuming this to be the case.

Does the ECU map not allow for the turbo coming in earlier and deal with ignition and fueling. I would imagine that the boost level would determine the fuel needed and ignition advance more so than rpm.

Sorry if the ECU can fuel and deal with the ignition advance a one particular rpm why cant it do it at another, lower rpm.

I just dont get this mapping stuff.

I'm off to design one that suits every mod I have plus any future mod I might make, LOL!!. Yeah right, like its ever going to happen!!

StickyMicky

mate i agree, ive never remapped mine yet

your maf sensor measures how much air is coming in and all the other sensors measure everything else.

if the standerd map cant handle say x amount of boost at x rpm then i can see why you would need it remapped, but for mild tweaks the standerd stuff has sum variance hasnt it?

i mean no 2 engines are the same so it must have?

Dark Blue Mark

I have HKS headers on mine, and full decat and although I haven't had it rolling roaded, It seriously flies compared to the STi4 I had with same mods minus the headers.... Not cheap though.

TEK3 on the way and off to PE rollers soon

MB

WRX_Rich

iTrader: (5)

talkin to a guy on here, he got lower results on a rolling road ( same day ) after fitting headers

was sorted after a remap

The Fixer

Your turbo will actuall spool later, the larger diameter tubing will slow gas speed down at lower RPMs but the headers really kick in when RPM rises because they are able to flow so much more gas than before.


Your ECU has two ways of working Open Loop Control and Closed Loop Control. Without going too deep I'll try to explain.

Open Loop Control

Your ECU monitors boost presure, MAF, MAP,TP(Throttle Position) and RPM, based on all these parameters it then looks at the fuel and ignition tables (like excel) and puts the appropriate(fixed value in table, entered by OEM or mapper) fuel & ignition values out to the injectors, ignition drivers etc. You will note that these tables hold "fixed values" which were entered by the OEM or mapper who last did your ECU.

Closed Loop Control

Your ECU monitors boost presure, MAF, MAP,TP(Throttle Position) and RPM, based on all these parameters it then looks at the fuel and ignition tables (like excel) and puts the appropriate value in the table, (entered by OEM or mapper) fuel & ignition values out to the injectors, ignition drivers etc
*Closed Loop bit coming. It then checks the Lamda sensor to see if the mixture is the correct AFR, if it is not then the "ECU makes adjustments" to either fuel or ignition to achieve the desired result. Usually find the ECU in closed loop in steady state conditions like cruising not mad foot to the floor acceleration.

By remapping we are changing the "fixed" values in the fuel & ignition tables to achieve the correct AFR during open loop control.

When ever you make changes to the air going into an engine or the exhaust coming out of an engine these fixed values need amending

Hopefully that wasnt too complicated lol

vulnax999

iTrader: (7)

Quite a clear and concise explanation of Mapping and how the ECU works in those modes Conrad... more !

The Fixer

I could tell you more but then we'd be out of business lol

robinH20MRV

hi m8,

i have roger clarke motorsport headers on my sti 8 ra, hooked up to a bob rawle full decat system, its still sounds good and goes like f**k!! though that may be more to do with mr simpsons magic fingers doing there stuff!!

cheers robin.

Tone Loc

iTrader: (1)

Ok get all that (not sure why all of it is relevant here) but if running a MAF based ecu the increase in air flow which results from the improved breathing will result in a higher load valued seen by the ecu compared to pre mod. So it will now be in a new part of the map not used before, depending on the car and it's oem map this may be ok fuel and ignition wise (probably not JDM STi).

I agree that a remap will provide gains in spool, if not using a dawes of MBC, but amending the fixed values is not needed. It will provide imporovents but the MAF is great at compensating for breathing mods.

Tony.

The Fixer

The explanation was due to the above reply

Upto a certain point, but the MAF's range was designed to work within the standard engine parameters, induction kits, breathing mods and exhaust mods can soon get the MAF maxed out or reading incorrectly, remapping may include a rescale of the values received from various sensors etc etc

Anyway, back on topic - back to headers ->

Tone Loc

iTrader: (1)

Still not sure where you're coming from. A remap is not needed.... while remapping the standard ecu i never got anyway near the MAF ceiling, even using the standard maps load figures. Increasing the boost from 0.9 to 1.3 bar, i was still not using the last few rows of the map (with a lot of breathing mods). For the above question i would have said yes the ecu will deal with the differences in breathing due to the MAF. However the standard map can be optimised to increase torque/power and safety (but this is also the case on a car without headers).

MAF are wounderful things

Tony.

The Fixer

Remember the standard map is there based on EURO emmisions and is therefor very very safe in terms of fuel, ignition & boost, bolting headers on and not doing the remap is not making full use of the headers. Surely its better to fit something and optimise the car to make the best of the parts fitted ?



Thats why most of the aftermarket ECU's and the higher powered cars have ditched them then? They are quite often the limiting factor

Tone Loc

iTrader: (1)

High powered cars like Andy F, Pavlo and Bob's Ecutek Sti5, 3 well proven high power cars . Don't seem to harm some very high power skylines either. What exactly would you say is the power ceiling on a MAF based car given it can be mapped to suit various MAFs then? What is the restriction your talking about.... diameter?

Tony.

The Fixer

Alot depends on the ECU in use and its abillity to give a MAF meter a new scale.

The diameter of the inlet pipe doesnt come into play in terms of a restriction until you are way up above 600 ponies. The restriction is in the ECU and its abillity to re-scale the voltage from the sensor into a range of air flowed that can be used.

Andy is using APEXi power FC which I assume copes well upto 600 HP, Bobs car running ECUTEK is 450 ish in reality before the NF mix is added.
Skylines, yes you are correct but did you notice they run two MAFS even on one turbo so they can try and measure how much air is going on?

We are way off topic here lol Somebody mention headers.....


Edited to add, what MAF's are useful for is to allow manufacturers to produce very envoiro friendly, safe running, mass produced engines out of the crate that can run within the OEM design criteria.

Tone Loc

iTrader: (1)

Can you name an ecu that you can't rescale the MAF on... i can't (including all OEM Impreza ECUs). So going by that you say the restriction is only above 600bhp... wouldn't complain about that (or agree with it either).

We are way off topic, but it was said that a remap is need to fit headers. I don't agree with that. A euro car will compensate via the MAF quite easily (and have an increse in torque and power), but as you say to get the most out of the car (headers or not) a remap is a good option.

A remap is most definately needed for a MAP based ecu tho!

Tony.

The Fixer

Where getting there then... lol The Subaru MAF can be rescaled upto a certain point I am led to believe. Hasnt John Banks managed to max his out a few times on the 2.5?

As for the 600 HP restriction on inlet pipe diameter I am referring to Subaru's and the work APS did in Auz where they found it to be a restriction above 600hp which is why there new DR650 kits are rotated mount turbo so they can get a bigger inlet pipe (or one without the flattened 90 degree bend in it)to the turbo.

Yes the ECU will compensate for the headers but it wont make the best out them either which is why we both agree a remap will make the most of them MAF or MAP based ECU.

Sorted

Bob Rawle

In actual fact the ecu won't compensate for anything, the values that are present in the open loop section don't change just because you fit headers and if they are not suitable for the load points then used cannot adjust or compensate in any way, only the closed loop section does that. So a map adjustment is needed. If discussing a maf with an 80mm barrell then it will more than cope up to mid 500's, the smaller new age gets pushed to the limit but a change to 80mm (as per my STi9) soon fixes that however a map change is necessary to rescale.

Equal length headers are not suitable for STi's as the cams don't work, non-equal length are best for sure, there are two/three manufacturers that make ad sell true equal length btw. Best for me has been those based on the Ion design but using proper flange couplings which overcome the gasket blow problems people have, these available from RCM. Primary and up pipe diameters are critical though.

And btw Conrad has no idea what power and torque I'm currently running off the oem ecu in the '5, it made just over 500 using Link or Motec, I'll publish some figures as and when. It will be six speed though.

And I always use Japanese grade fuel in my JDM cars and always will, Andy uses Scottymax iirc.

cheers

bob

The Fixer

Bob, only guessing at 500 HP for your STi 5 based on figures banded about on here and 22B, feel free to correct me if its wrong. Your car was brought up by Tony on regard to MAF's nothing else.

Tone Loc

iTrader: (1)

LOL, compensate was probably the wrong word to use. Think everybody is saying pretty much the same thing tho but in different ways.

Group buy on headers anybody?

Tony.

Andy.F

MAF's are only a limiting factor if they are wrongly sized to the application, just as a MAP sensor would be.
MAF is far superior on a turbo car in my opinion. This is with regard to the self compensating nature and potential power output.

Andy

Tone Loc

iTrader: (1)

Andy... no no no, do not use compensate .

Tony.

U WOT!

Yes please.