Discussion in 'Technical' started by gururajanv, Jun 2, 2010.
11-12kmpl is fine for a tjet
Thank British for that.
That is right. I have first hand experience of this, after two or three curves, you won't see any one in your RVMs unless you stop and wait.
i find the fiat's state of tune such that it will ensure longer engine life. the way the swift behaves i feel that its good for short time fun but in the long run the engine will not perform like the fiat.
Great thread! and great explanation regarding shorter gear ratios in the Punto / Linea.
Now, can somebody throw light on the engine tuning differences between Swift and the Punto as well? Or is that OT?
@Gurjinder, I think you are the right guy to explain this.
from my experience of driving a swift VDi i think the tuning is done in such a way that in lower rpm more fuel is pumped and the turbo FGT is given max boost at around 1800 rpm with max fuel qty i.e rich mixture and as the rpms rise about 3000 the tune again goes to lean.
in case of linea its very much evident that the tune is lean till 2500 rpm and riches out much after around 3000-3200 rpms. turbo boost is also linear and not a full boost at lower rpms.
if i want to tune my linea i would map it in such a way that more fuel in lower rpms with more boost and then ease out 2700 rpm onwards. again at 3500 plus rpms i would like full boost. my economy range would be 3000 plus/minus 150 rpm.
Thanks Sat , i am very much humbled by your gesture.
But having driven a Punto once for about 4-5km's only , i can't really comment on what differences are felt between the Punto and Swift while driving them.
But one thing which was easily noticeable was that the Swift has a "peaky" power delivery , that is , it peaks suddenly. The Punto is more gradual , and hence more predictable. That Swift surge is good to experience once in a while , but it's not exactly a good thing during routine drive. ( I've stirred a hornet's nest)
@Italia Linea - Swift D is all turbo lag uptil 2200 rpm. Only after this does the surge start.
And it's not all about the air-fuel mixtures as such. In a turbo diesel , the behaviour/ response is dependent upon when the turbo spools up to the required revolutions. You cannot just put more fuel in and expect the turbo to provide max boost as a consequence. The turbo is a mechanical device, and it will give you the boost it is set to give only when it starts spinning at the required rate.
You can put extra fuel before the turbo is at its max spool and all you'll see is black smoke from the tail-pipe. Tuning boxes do this sort of thing, and that's why you see much more smoke and soot off-boost.
The Linea's turbo, being a VGT is in it's happy zone after 1800rpm , and from then on it's linear power delivery to nearabout 3.5k rpm ( I've tested it upto 3.5 only as of yet)
There is a trade off in getting turbos to perform well at lower rpm's , middle , and high rpm's. A turbo good at low rpm will most probably be bad at higher ones and so on.
Most passenger cars will have either one of such turbos. Only in performance turbo cars would you find turbos performing well from almost low to high rpm's. This is when you enter the field of sequential turbos and the like.
So , unless you have the turbo to suit your needs, extra or less fuel here or there will not make much difference.
OT Just a friendly advice, nothing to offend you my friend -
Automobile is a piece of engineering with hundreds of intricate parts working in tandem. Sometimes you may or may not notice its abnormal behaviour. At times you may even construe normal behaviour as abnormal one. So try not to diagnose the car with a electronmicroscope...
So I would say relax and try to enjoy the car, driving pleasure and enjoy the driving till the car is driving good. Remember at the end of the day its a machine and it would have its end day. So enjoy the car before its expiry period....
@ Gurjinder, agreed with you.
But the fuel qty also plays a important role in a turbo diesel. the whole tuning is dependent on this important parameter.
The amount of power generated by any Diesel engine is directly proportional to the Fuel quantity that is injected into the combustion chamber.
But it atleast needs 18 times more air at every given quantity of fuel injected for a proper combustion without smoking.
A Turbo spools only when it has enough flow of exhaust gases which again is dependent on AIR/FUEL ratio.
At 2200 rpms as you say when the turbo overcomes full inertia the fuel qty is also more making it more rich and so the power delivery is more.
The fuel tables in the ecu at 3000 rpms and around at lean as turbo has overcome the inertia and can give perfect A/F ratio for smoke free operation.
The formula that i remember ( correct out if i am wrong- old memories) for turbo airflow for desired HP is as follows
Airflow (actual) = Horse Power X A/F(airfuel ratio) X Brake specific fuel consumption in minutes
similarly the Manifold pressure required for same HP is also very important and also has some formula, but that i dont remember- i hated that during my engineering , LOL
but the above Airflow is used as parameter in Manifold pressure
in the whole calculations of diesel engines Fuel qty is very important parameter unlike Petrol engines where ignition timings play the most important role.
in case of Lineas VGT, due to the turbo spool at low amount of exhaust gases at 1750-1800 rpms the fuel curve immediately starts soothing out as the inertia is overcome.
Thats why i said that i would love to put in more fuel for a prolonged rpm range within safe limits of EGT(exhaust gas temperatures) for quick pick up and performance on linea in lower gears where rpms go above 3000 and while cruising on highways these can be eased out to more till speeds of say 120 where rpms is around 2500-3000.
anything above that rpms again should shift to rich fuel maps and more fuel = more power after 3000 rpms to overtake in breeze.
Regarding turbo- a VGT turbo is anytime better than a FGT turbo. it is a turbo that is good in low rpms as well as high rpms.
Performance turbo cars run very rich and have higher engine capacities so they require and can run a dual turbo or a sequential turbo or a hybrid turbo.
on smaller engines below 2000 cc VGT is the best and FGT is the very basic.
Currently linea is remapped perfectly for more fuel efficiency across the range considering the fuel quality and 90bhp desired output.
so if you want performance you need to remap it but in performance range more fuel consumption will occur and to compensate this one can become more lean in cruising speeds.
But in any case this remap will be deviation above the design tolerances of parts involved and can be good if done in correct tolerances.
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