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Discussion Starter · #1 ·
guys, bear with me on this 'cos i get confused by all this.

I have been looking at the RC stage 2, 1.4 bar and ~350bhp using AVCR and amp; s-AFC, cost is around 1800 fitted. Dragon have offered me a similar but not identical solution.

From the gems thread in Lancer Chat, it seems that i can achieve the same power, i.e. 1.4bar but also not sacrificing torque for around the same money (under 2000). And also maybe fitting an uprated fuel pump as well. Is this correct, or am i missing something ? If the cost is similar then i prefer the gems route since it is neater, more options and better for future power mods.

If i then went further up to 1.6, 1.7 bar (380bhp -ish) with the gems what internals would it be advisable to uprate, and what would the costs be ? (pistons ?, conrods?, cams?, crank ?, intercooler ?).

Finally, how much is the Motec over the gems and is it worth the extra (apart from just the kudos of the name border|EQU| 0 align|EQU| middle > )

sorry for all the questions, feeling a bot confused by it all.


Discussion Starter · #2 ·
Jackal, we could save a lot of time if you just gave me a call :D

I would suggest that you do not go for the AVCR and S-AFC set up unless you particularly want adjustable in dash boost. The S-AFC tricks the standard ECU by clamping the signal from the airflow meter, adjusting it by |PLS|-50%. The GEMS is a proper ECU that allows full mapping of everything. The Motec is the same, and the difference in features for application in the EVO are hardly any at all. HKS Europe have back-to-back tested Motec and GEMS and get identical power results on the same highly tuned EVO. Motec costs more, but doesn' t have idle control or knock control as standard - whereas GEMS does.

GEMS is £1395 supplied, mapped and fitted. With GEMS you can go to ANY power level as you have control of fuel, ignition and boost at all RPM levels. The SAFC/AVCR combination is limited for a whole range of reasons, but good to around 400bhp max. The GEMS/Motec route also allows you to dispose of the airflow meter and go for a MAP sensor instead - which removes the restriction from the air intake that the airflow meter (MAF) provides. Boost pressure does not give a straight correlation to power - it is the sum of many different things. Custard, for example, has 390bhp ish at only 1.5 bar! My car is producing 400bhp ish at 1.4 bar (different turbo though).

Power comes from improved efficiency through better flow, mapping etc, and boost. Torque mainly comes from increased boost pressures. Being able to map the boost at rpm levels is important - you can get the most out of the turbo at all engine speeds. Constant boost is limited to the maximum boost a turbo an hold at high rpm. The standard turbo is really only ok to about 1.65 bar at 7000rpm, but at 4000rpm 2 bar is possible. Running constant 1.65 bar means you lose alot of power in the midrange. RPM mappable boost is only possible with a full ECU or the AVCR. Standard internals are ok to 1.7 bar, but you are running at the edge of their reliability envelope. I would stick to 1.55 bar on standard internals, at all rpm speeds. Above that, upgrade the internals, particularly if you sustain high rpm loads, or high midrange boost (e.g. trackdays, rpm mapped boost). Upgraded internals for strength mean pistons and rods, and replace the crank bearings while you are at end - balance the bottom end at the same time. Uprated head gasket too.

On the cam front- if you want a more cammy engine, then upgrade that - pushes the power band higher up.

Powers above 350 bhp demand a better clutch. High torque does too - something like the CUsco twin plate is excellent as you get a lightened flywheel which makes a huge difference to engine performance, particularly as higher boost often implies a slightly reduced compression ratio.

Intercooler - mmm - I don't think so, unless you go over 450bhp.

Uprated fuel pump? Not before about 350bhp also - just rewire it.

Remember - all of this stresses your system. My approach was to uprate everything first and add safety devices, like water injection, BEFORE turning up the power.

If you want to chat in detail, happy to share what I know. Drop me a mail with your number, and I will call you.

Discussion Starter · #4 ·
initial map is £500, not sure about tweaks after that. Substantially less I would say, but I am guessing.

Discussion Starter · #5 ·
I'm debating right now how often I will need to get the ECU remapped or even tweak it myself, any thoughts?

I'm guessing it won't need to be changed too often, that being the case I'm thinking about GEMS again :(

one day I'll make my mind up

Discussion Starter · #6 ·
Bet you don't make up your mind! :D

I have heard from so many people now good things about the GEMS and Steve Simpson. Tech specs are not enough for me anymore. Nothing beats recommendation. Proof of the pudding and all that...
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