20VT- BHP limit???

Nyssa + Paul - you can include me in this as well. If you push your car anywhere near a perceived limit then you need to be prepared and have a few grand in the bank for a rebuild....

I agree, having an engine 'go' on you will change your preconceptions somewhat, however, I would like to throw is some more fuel to the 'fire'

Of the engine failures that occur on the Coupe, they fall into either piston or rod failures.
Almost all the engine failures are piston failures.
I'm not including turbo faliures as this is obviously something different.

Now if you look statistically at the piston failures, I'm sure Rog and Barbz would agree, they tend to occur in standard or 'lightly tuned' coupes, those running plug and play chips and standard turbos and intercoolers , although statistics can be misleading as most of the Coupes may well fall into this category by numbers alone.
So whether this is due to incorrrect engine mapping, or excessive charge temperatures, or a combination I don't know.

However look at the number of higher powered coupes running proeprly mapped cars roller bearing turbos etc, and you can see that quite a number are running 300bhp+ for some considerable time now.

Of course there must be a mechanical threshold, even with cars running water injection etc, but where this is??, I mean how many failures at 350bhp+ have there been?, I mean seriously, how many?, hardly any in truth, but then the number of cars running 350bhp+ are scant and few, so its hard to make definitive information.

Ones I can think of, is Fergies car on the rollers, being put down to mapping and very high overboost, then there's Barbz 'experiments' with NOS and again very high boost levels, JohnS, and err can't think of anyone else.

Still, having a piston go, is very unfortuante and expensive, and running less power should surely increase reliability, but maybe not as much as you think

With the rod failures, there's Nyssa and JohnS, both showing failures along the 400bhp mark, but with two cars again it gives an idea only, but again likely to be somewhere less than this.

Joe

I think most of the cars running 350 odd bhp are already running replacement or rebuilt engines, wheras the 'lightly tuned' cars are generally those running on the original engines, which are in some cases nearly ten years old.

an interesting thread, and vibes i'm picking up are that an FMIC would be a good move.

I think, that blown pistons mostly are caused by wrongly mapped cars. Because of too high exhaust temperatures Aluminium will lose stability dramatically - the beginning of the end of pistons...
To the rods - investigations in Germany showed that the quality of the rods is fluctuating.
Thus rods could be found with visible forge-defects... Nevertheless Fiat mounted these inferior parts.
A good idea particulary for older rods may be shot-peening -this method definitely will show damages / cracks with a positive effect of higher durability.

Juergen

The rods weakness is torque and quality of manufacture which is *very* variable in my own experience. The pistons weakness is the ringlands which are visiually less substantial than a lot of comparable turbocharged engines' cast pistons.

If you're tuning your car you have to either determine what your safe limit is or be willing to take the consequences of going over it. Since there isn't a great deal of empirical evidence all you can say is 400BHP and 400lbs/ft is almost definitely too much. 360BHP and 360lbs/ft is only 10% less so is probably around the range of limit where you must be willing to take the consequences, and anything below that is much more subjective.

If I was starting again tuning a std 20VT I would put forged pistons and rods in at anything over 330-350BHP as there are other benefits to them too, like they weigh a good deal less (>20% less), they are balanced to within 0.1g compared to Fiats +/-5g and they can take a little more abuse without breaking if nothing else. And given that the bores on the turbos tend not to go oval much it means that even a relatively high miler can chuck them in safely (after inspecting the bores) unlike on some other engines.

Does anyone know what is deemed the peak EGTs we should see on our engines??

Jamie

I read the other day, that 900-950 was the most you should get, before you start getting into trouble.

I've read similar figures, but then they also referenced overfuelling causes the EGT to be higher when I would have thought lean running would give higher EGTs

Jamie

well just from my nautical days when i used to work on 6000bhp diesels that had individual fuel pumps if we had low exhaust temps on one cylinder we used to put that fuel pump on that cylinder to full fuel to get the temps back up so sounds like too rich gives high exhaust temps

Kev

Jamie, when I've been reading about EGT's almost all the information on the web is from diesel engines, aiplane marine and large trucks.

I have also heard there is 'optiimum' fuelling for ideal EGT's and that 900-850 is the ver ymax that should be tolerated, ideally less than 900 degC

Joe

Depends on the head design as well as the engine. The 20VT sees highe EGTs due to having relatively short exhaust ports in the head (ie. the gases get cooled less in the head).
I usually see around 800-900 at 7300rpm, although have seen as high as 940. My EGT guage has a peak hold and the highest it has ever been is 963C which was when I had a fuelling problem (pipe off the pump came loose somehow). If you have sky high EGTs it can be because you have a lean mixture as well. All those temps are without my aquamist on which makes a bit of a difference.

John, I've tried to make comparisons between aquamist on and off, but its hard as my aquamist is boost activated at 1bar or above, however I find I get higher EGT's running 0.9 bar with aquamist off, as compared to running 1.1bar with aquamist on? so I presume that the water injection does seem to make a difference.

regards

Joe

Joe, just unplug the pump so you have no water flowing and then see what temps you get. I would be interested to see what difference it makes as it is a safety mechanism as well as for power. Since you have had your EGT gauge has it ever got dangerously hot where you have backed off? I guess the true test will be on the track after a few hot laps.

Not sure what EGT guages everyone has, but on mine you can set an alert temp which causes a built in red light to flash, and an alarm temp which could be wired up to a boost controller to turn off the controller (ie get base boost) if it goes off. I currently use the alarm to trigger my intercooler waterspray

I've seen as high as 910 at redline giving it some welly, but not sure if this is good bad or indifferent

Jamie

The highest EGT, we noticed at an original 20VT without any chiptuning, was 940°C (on a german autobahn at wot 260km/h for 5 minutes, ~ 25°C ambient temp.)
Therefore I think, that 950°C are still ok!

Juergen

Ok, when I have my Unichip sorted I'll post up peak EGTs after that for comparison

Jamie