Tuning Fiat Coupe 16V Turbo for economy

Road-race engines and ancillaries - general discussion
kj16v
Posts: 15
Joined: June 18th, 2008, 6:08 pm

Tuning Fiat Coupe 16V Turbo for economy

Post by kj16v »

Hi all, I'm currently attempting my toughest project yet - trying to get decent fuel economy from a Fiat Coupe 16V Turbo!

As above, I am trying to tune my Fiat Coupe 16V Turbo for better fuel economy - without luck so far.

My setup:
TunerPro RT editing software
Winlog datalogging software
TechEdge wideband lambda
det-cans (for listening for knock)

I have already leaned fuel to 15:1 afr at steady cruising conditions (2500rpm-3000rpm, 0.4bar-0.6bar absolute). This hasen't made a dent to cruising fuel economy. Can anyone tell me whether it would be 'safe' to lean steady-crusing as far as 15.5-16.0 afr, as long as there is no knock?

As yet I don't have an egt sensor. Do I need to know egt to be able to lean the mixture safely?

Would it signicantly improve economy (due to better fuel atomisation?) if I increase the fuel pressure to 3 bar, from the standard 2.5 bar (and of course adjust the fuel map accordingly)?


Thanks in advance for your help.

By the way, before anyone mentions it, I already know being light on the throttle helps thanks!
Guy Croft
Site Admin
Posts: 5039
Joined: June 18th, 2006, 9:31 am
Location: Bedford, UK
Contact:

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by Guy Croft »

You're taking a big chance leaning out the fuelling to try and improve economy!

GC
Julian
Posts: 181
Joined: June 22nd, 2006, 6:45 pm
Location: Manchester, UK
Contact:

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by Julian »

Your best hope - in my honest opinion - for improving the economy is not to try and simply reduce the fuel consumption per stroke of the engine, that is a potentially dangerous thing to do (for the engine at least). Instead I would suggest looking at the factors that waste the power produced and if you want to get technical it can be done within the engine bay (there is the usual ones like incorrect tyre pressure, poor wheel alignment, excess weight carried, poor window and door seals etc - all of which are very valid).

Turbo engines tend to be low static compression to compensate for the much higher dynamic compression that comes from supercharging, you already know this but it is a relevent point. In terms of driving style, if you can keep the engine off boost you will use a lot less fuel simply because the AFR doesn't require it. This doesn't sit well with a lot of people though and it really can be a tedious job keeping the boost down, especially on motorways. The alternative from an engineering point of view is to increase the efficiency of breathing so you don't need as much boost to reach the same result. Traditionally methods for improving flow characteristics as applied to normally aspirated engines are equally valid here, better gas flow means a more efficient turbo charger, less waste heat, better reliability and ultimately less fuel consumption but to really take advantage of this you will need to consider an increase to the static compression ratio of the engine.

There is a problem with this - such changes don't tend to come cheap and while I appreciate that fuel is becoming more expensive (by the minute it seems) you will need to do an awful lot of miles (or make some revolutionary breakthrough in fuel economy) to actually see a positive payback on the work invested in.

There are alternatives. LPG is still roughly half the price of petrol and a four cylinder install will set you back about £1000, you can make that back in a year for the average yearly accumulation of travel. Brown's gas systems seem to be showing their head again and offer a worthwhile improvement in economy (if they work - I've only met one person who has actually installed one of these and proven to me that it isn't just a lot of hot air but I remain unconvinced - call me a cynic but it seems to good to be true and we all know where that adage ends).

In terms of simple mapping your only real hope is to work out where fuel is being wasted rather than just altering the AFR, it isn't a simple task but it is possible. The real difficulty is that manufacturers have really tightened up on this sort of thing in the last 20 years (pretty much since the widespread adoption of mappable fuel injection) so there isn't likely to be much you can save.

A simple clean of the injectors might actually prove more cost effective (I don't mean a can of STP in the tank - I mean a proper injectors out, sonic clean).
kj16v
Posts: 15
Joined: June 18th, 2008, 6:08 pm

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by kj16v »

Thanks for the reply Julian. I suspected as much. Trying to get better fuel economy out of such a low compression engine (8.0:1), without actually raising the comp, is flogging a dead horse.

The first thing I wanted do before tuning was to clean the injectors but, as far as I can see, the injectors are impossible to get at without dropping the engine out.

As for Browns gas: I'm impressed you even got one person to show it works. I just had a quick look on the net. Shame you're not allowed to link to other sites here because some of the schmience spouted is - amusing - to say the least.
SteveNZ

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by SteveNZ »

You only need to remove the inlet manifold to get to the injectors, but that is a bit of a task. When they designed that engine I doubt fuel economy was ever a factor. Even with higher compression, Tipo 16Vs for example dont get great fuel economy.

Altering the AFR at cruise wont help much as you have found out; the engine is already using minimal fuel and should be in closed loop anyway. To use significantly less fuel you need to reduce consumption under heavier load conditions, and that is more dependent on weight.
Evodelta

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by Evodelta »

In general the same things which improve power also improve fuel economy.

Improving the airflow from the air filter to the end of the exhaust pipe:

Free flowing exhaust

Clean air filter

Gasflowed head

Efficient intercooler

As mentioned, higher CR

A mapper who knows what he is doing.



Also correct tyre pressure and geometry

Brakes which don't drag

Good bearings

Aerodynamic aids (How many Coupe owners remove the flat engine undertray??)

A driver who can drive smoothly and economically.
BasilBadger
Posts: 4
Joined: May 12th, 2008, 10:32 am
Location: Denmark (3670)
Contact:

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by BasilBadger »

Hello everyone,

Working on a friends VW Golf II GTI 16V, that had unsatifactory fuel economy. We had a somewhat unexpected but very logical suggestion from the chief mechanic at the local VW garage:
Make sure the injectors are matched, giving the exact same amount of fuel!
We achieved this by building teststand from a standard fuel pump and a burette. Simply measuring how much each injector flowed over 30 seconds. A timer and a resistor in series with the injector is also needed.

The explanation we were given goes as follows: The engine mangement system, which incorporates a lambda sond, will try to achieve Lambda=1. If one injector is, say, slighty low, then the ECU will compensate for this based on an average. Hence the other injectors will fire slightly longer. Making the whole engine achieve Lamba=1, but with each cylinder being slightly off.
As a consequence all cylinders will run at a lower effiency and this impacts noticeably on fuel economy.

We ended up bying ten new OE injectors, selecting the four that were the closest match. Fuel economy has improved, though not enough to offset the cost, I am sure.

All the best,
Henrik
33
Nobby
Posts: 87
Joined: August 24th, 2010, 11:58 am
Contact:

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by Nobby »

For those not on the Fiat Coupe Club UK forum (FCCUK.org) - It has been proven by a long standing member of the Fiat coupe club uk (Nigel) that a well modified cylinder head has given him excellent fuel economyw with a combination of other performance modifications.

I should also point out that Nigel owns one of the most powerful Fiat Coupes in the country (running around 450bhp/380lbft, 2ltr 20vt 6 speed, C&B cams, mapped by FC performance). He consistently achieves over 30mpg and 400+ miles per tank. He even calculated how many miles he would need to do to ofset the costs of the headwork ~ around 30,000 I believe.
Chris Burgess
GC 01
WhizzMan
Posts: 459
Joined: August 13th, 2010, 8:05 pm
Location: Amsterdam, the Netherlands

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by WhizzMan »

The 20VT is based on another engine entirely. That being said, proper porting the head and matching injectors will help on any engine, if followed up by proper setting up the ECU.
Book #348
Guy Croft
Site Admin
Posts: 5039
Joined: June 18th, 2006, 9:31 am
Location: Bedford, UK
Contact:

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by Guy Croft »

I'm afraid that tuning a turbo unit for power (as with Nigel's mentioned above) and tuning an atmo unit for power both bring a fuel consumption penalty.

The only way to make a gasoline turbo unit truly 'fuel efficient' is to run the turbo on max rated boost all the time. That compensates for the low CR and makes best use of the exhaust energy. Trouble is (!) that doing so produces a lot more power than an atmo unit for given cubic capacity and so a lot more gasoline is needed.

I think that is called a 'conundrum'?

GC
NickRP
Posts: 126
Joined: September 28th, 2006, 3:26 pm
Location: Nis, Serbia, Europe (A)
Contact:

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by NickRP »

I agree completely.

My two cents: there is a possibility to improve turbo charged gasoline engine fuel economy by about 15% (at higher load) to 20 % (at lower load) by introducing EGR. This is, however, not a trivial task and rarely can be done satisfactorily within a scope of a typical DIY project.
GC_98
WhizzMan
Posts: 459
Joined: August 13th, 2010, 8:05 pm
Location: Amsterdam, the Netherlands

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by WhizzMan »

NickRP wrote:I agree completely.

My two cents: there is a possibility to improve turbo charged gasoline engine fuel economy by about 15% (at higher load) to 20 % (at lower load) by introducing EGR. This is, however, not a trivial task and rarely can be done satisfactorily within a scope of a typical DIY project.
And to think that most people tuning the 16V turbo as in the coupe and Integrale immediately kill the EGR.
Book #348
andy wright
Posts: 38
Joined: September 6th, 2010, 4:43 pm
Contact:

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by andy wright »

Evening,
Fascinating discussion. Although the logic is somewhat bizarre,if you want to make your turbo engine use less fuel by a combination of gentle driving and little boost (where clearly the efficiency will be low because the CR is low) you might be better off building a N/A engine following the ideas in Guy's book!. I plan to build a replacement engine for my Integrale over the next 12-18 months. I will ask Guy to do the head. My thinking is, by appropriate choice of cam, excellent airflow through the head, OE turbo which does not have a huge compressor and careful build of the block that it will be possible to (after mapping) have an engine that boosts from a low RPM (to get the CR up) but not huge amounts of boost so that the power output at, say 3000rpm is useable and not frightening and still, if needed(!) have power and torque in reserve by the use of the overboost facility in the Eprom.
That's the dream. I am not sure if it is possible, but it will be fun trying!
Andy
GC_20
WhizzMan
Posts: 459
Joined: August 13th, 2010, 8:05 pm
Location: Amsterdam, the Netherlands

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by WhizzMan »

You might want to consider a "small" ball bearing turbo for that setup. It will spool quicker and easier than the stock turbo. This will allow you to run with less throttle and at lower RPMs, without experiencing an uncomfortable turbo lag. As long as it's big enough to provide air for the power you want the engine to deliver at full throttle, you should be fine.
Book #348
andy wright
Posts: 38
Joined: September 6th, 2010, 4:43 pm
Contact:

Re: Tuning Fiat Coupe 16V Turbo for economy

Post by andy wright »

Evening,
Good point. The roller bearing turbos generally seem to be linked with much higher power capability. I had not thought of your suggestion, which would make an excellent compromise.
Andy
GC_20
Post Reply

Who is online

Users browsing this forum: No registered users and 32 guests