simple mods - more harm then good

[lofty]

i had a glance through a scooby forum the other day, its well know that the standard scooby exhaust and air box is restrictive, therefore when they do the same simple mods we all do (exhaust & induction kit) there is a good improvment but....... one thing that seems aparent is that when people are fitting after market exhaust and induction kits they are increasing the air flow (as desired) but it means they run very lean and down the line this causes the inevitible big problems, what the all seem to say is that a remap (increase in fuel) is very important if your going to do even these simple mods.

what im thinking is that our cars arent that restrictive from standard so the simple breathing mods we do dont make much differnce, but what little differnce they do make (if any) is simply it runs lean at high revs lean because of the slightly increased air flow. In effect the benefit will be minimal and possible long term damage with a *good* system,

how many peole are running such mods without the increase in fueling i.e a chip? and also these chip are designed for a best fit type approach, i.e they have been designed to increase fueling slightly but its basicaly a guess because the state of the breather system isnt known, so they are designed as a best fit.

i just struck me that alot of the traditional route of modifing cars is rather inaccurate and "near as damn it"

i know its very cheap to get a mass produced chip rather then have a compleate remap with all the costs involved and the time on the rollers.

it must be true to and extent because of what was first found with 172 induction kits, (they increase air flow but cause the engine to run lean at high revs)

how much of a problem is this? and should we all leave our cars standard or modify them all at once with massive one off costs?

 

[maciek]

phew i think the Reno original sowtware should be able to cope with those vast amounts af extra air. It has map sensor or other means to measure it.

It;s just that almost all modern cars are calibrated leanish. - that;s why chipping givs some power.

 

[Roamer]

Well, I got my zorst and viper at the same time, then a few weeks later got it remapped down at Power Engineering/London Superchips, and Im glad I didnt leave it any longer, it was running lean top @ WOT, so Id say no, the standard ecu mapping cannot cope with it, even though it has a map sensor - get it checked and remap if necessary, I beleive Chris172 had slightly different results to me, but it still had fueling problems (Must be the ducting diameter - I wish I hadnt said that now, all hell could break loose!)

 

[BenR]

yup, teh RENIX system on teh clio dont ahndle it too well, as i found out too....

but funny you call the bolt on stuff traditional mods.

in the 50s to 70s most people would swap head, carbs, manifold, dizzys, mod advance weights, etc etc....so, i think as time has progressed, the average max muppet has given modders a bad name as intelegence has decreased and bolt on mods become the norm.

i dont call this progress.........

 

[JoZeFF]

I think Lofty is absolutely right. I mean is it really worth going from 172-180hp and risk damaging an already highly tuned engine? I mean common guys, 8hp... can u really feel the difference??? it will decrease ure times by.002 of a second perhaps??? is it worth the money/ voiding the warranty???

I mean, if we had turbocharged engines like the 1.8T in Golf Gtis, audi A3s which are apparently detuned and can be chipped to get HUGE power and torque increases it might be a different story. But common... 8hp......

 

[Pysco]

Here Here Ben, spot on!!!!!

 

[Steveold]

If it was only 8 bhp then why is it claimed 10bhp from just putting a viper on ya 172?????

 

[silou]

because it is bull sh*t it is all about selling.

 

[Nick Read]

yeah some good points. In theory a fuel injected car should read increased manifold pressure from a higher-flowing air filter and adjust fuelling accordingly. After all it has to have this capability to account for differences in air temperature, altitude, gradual clogging of the factory filter element etc. And its not just for the sake of giving best power, its for emissions so you know theyre gonna try and get it right and use an ECU capable of adjusting the fuelling to account for all kind of variations.

My personal theory is that the normal ECU can deal with fuelling issues like this at low revs without any trouble at all. Assuming were talking about a performance air filter, all the ECU has to do is increase the injector duration to keep the air/fuel ratio spot on. If the lambda sensor tells the ECU its gone rich, then the ECU lessens the injector duration. If the lambda shows lean then the duration is increased.

At high revs though, there will come a point when lengthening injector duration cannot be achieved any more...because the injectors are open 100% of the time, trying to supply the fuel to compensate for the amount of air being drawn in. Naturally if the filtering medium is flowing more air, then this too much air effect will be more pronounced the more the engine is trying to pull in (at higher revs). Now the only thing the ECU can do is adjust the ignition timing. There is no physical way that any more fuel can be put through, so the engine eventually starts to run lean. Of course you could always fit bigger injectors or increase the pressure at the fuel rail. But were talking about ECU work here. Its no wonder that 172s with filter mods run lean at the top end, it is pretty much what you would expect. Maybe Im wrong though, but this just seems to make sense to me.

 

[Steveold]

Thing is when you buy a 172 its already pritty well tuned standard... When people mod normal cars like the 1.2 - 1.6 clio they will have more of a gain by adding a filter, exhaust and remap as those engines are made for being ecconomical. 172 from a 2.0 16v VVT engine is pritty good. best thing to do to that engine is a turbo or nitrous!!

 

[ChavyBoy]

OK heres a question why not fit another inject into the plenum chamber and when the normal injectors are running at 100% capacity and you need more fuel the 5th injector cuts in a feeds all the cylinders with the extra fuel ?

You would of course as many people said need to know specifics like air flow in and air flow out at WOT if you fit a non standard filter and free flow exhaust.

If you are running an induction kit by itself and a standard exhaust I cant see this making much difference after all you can get the fuel in quicker but you cant throw it out any quicker I would hope the standard ECU would take of leaning up the mixture.

 

[BenR]

because the 172 comes with 166bhp as std.......from teh factors as teh factory have told us and we have tested....so, its not just 8bhp. the amount of development i went thtough with the chip alone left the car driving much better......but overall power gains were not huge, and dont really decrease 06- times....its all fun and games really....would we of bought a 172 if we werent interested in power?

 

[steve_rt]

nick - great explanation, really cleared it up for me!

but the topic raised, although aimed at 172 owners, has worried me a bit! I suppose if the 172 ECU cant cope then the 1.4 Phase 1 ECU is definitely not gonna cope?!

Also, how can you tell when a car is runnign too lean (in driving terms?)

 

[BenR]

CO readings.......sniffing the tailpipe dont work to well.

as for the ecu, i woudnt worry too much, the 172 is a much more complex and dedicated item....just cause its less powerful doesnt mean its any more likey to break,......itll probably last longer actually.

 

[Steveold]

mine pinks!

 

[JoZeFF]

Yeah, but thats not the point!! we bought the car for power the way it is.... its tuned almost to its max.... and is reliable the way it is isnt it? I mean, would you really risk possible engine damage trying to squeeze a tiny bit more out

 

[HongKongClioman]

I think Joe had earlier posted a picture showing the damage caused to the head by lean burn. Worth looking.

 

[BenR]

that was pre ignition and you could see where it was sourcing off the same area in the squish area....but that was running seriously lean, and we corrected it before anything happened so, so, im not afraid to do anythign to the engine.

the engine can safely run 215bhp on Tbs as we fitted to our cup race in Zhu Hai, the inlet manifold is that restrictive. and thats std cams, but with magenti marelli 3d ignition modelling.

reliability is only the result of proper tunning, we could make the 172 run 50bhp really badly.......

 

[Nick Read]

Steve, running rich or lean will rob power, the further out you go, the more you lose. As a basic rule of thumb for best power and economy you need to be at the stoichiometric ratio, 14.7:1. However different engines vary from this slightly and it tends to be that most engines will make full power at slightly richer than this, say 13.5:1.

Running slightly rich isnt a problem at all really (in terms of engine safety). Running lean can be a big problem. Without going into the details (Ben can explain all the different issues) you just do not want to be running lean. you can check this by hooking up an air/fuel ratio meter to your lamda sensor and driving around with it on the A pillar right in front of your face. A certain someone a while ago took the piss out of the idea of having an AFR to keep an eye on things...but to most normal people, actually *having* a rough idea of where your fuelling was would be preferable to complete ignorance of it. The only other way to check your fuelling on the road would be to have a gas probe up your tailpipe the whole time and a gas analyser in the boot or something and a load of wires everywhere.

 

[BenR]

the means of running rich or lean is far more cloudy today than ever as most engines head will be desined to run on leanburn technologies and make just as much power. so, lean and rich is relative to your engine and where it runs best.

my kent likes to run rich, but teh late 80s leanburn CVHs will run nicely on a leaner mixture........so, dont worry about what your figure is too much, just make sure your motor is running sweetly.

 

[Nick Read]

Yeah thats what I kind of meant by the thing about engines varying slightly. Theyre all different so just get it running right and youre about there.