As the plugs in the Rangie appear to have been in it for about 3 years and are beginning to die I thought I'd ask on 'ere if anyone *knows* anything much about plugs and turbo engines.
Engine is blueprinted, low compression EFi 3.5 Rover V8 running around 7 psi of boost. I've not pulled the plugs out yet to see what they are due to the sheer amount of time it'll take to drag the bloody things out - Carl, this is one of those times when you'll be thankful your V8 is so easy to work on..
Space is somewhat limited on O/S bank, like so
formatting link
As the conversion was done the best part of 20 years ago, hopefully plug technology has improved somewhat and there may be some new fangled (but not hideously expensive) Überplug that'll work better than the old ones and last a bit longer - they're that much of a bugger to get at I don't fancy changing them on too much of a regular basis.
Any pluggists out there who actually know what they're on about, or is this thread just likely to descend into the usual "NGK vs Bosch" argument?
"Pete M" wrote in message news:f3npre$ta8$ snipped-for-privacy@registered.motzarella.org...
formatting link
My new plugs cost me £60 for 4 so I doubt you wanna put them in, but the Bosch Super 4 seem to be good for the money, 4 electrode jobs, eBay is the best place to get them, they are made for all turbo cars.
First some theory: in a turbo engine the mixture is more dense, more turbulent and most of the times a bit hotter than a NA-engine, conditions vary more too.
So in order to ignite correctely the "more difficult" mixture, the ignition module on a turbo engine produces a stronger spark of longer duration but as it is stronger than on a NA-engine it "eats" away the positif side of the electrode.
Now real world: any plug will do but you order them a degree colder than for the standard NA-engine. IF you are a tight bugger (ain't we all) you order normal plugs, if some else pays for them (and not your GF) you order platinum plugs (they resist the abrasif flame better)
What is the colder plug? The one with less or a smaller amount of ceramic around the electrode. If you go too cold, the engine will start difficult and the plugs will foul with carbon.
Plugs too hot will simply die, sometimes you see nothing on them another times the complete electrode is gone. Bad idling can occur too.
How you know that plugs are NOK? From a no-boost situation (low RPM) you floor the pedal. The engine will pick up but misfire or cough. If you can see any reduction in thickness on the electrode, it is time to change.
Before installing the plugs make the gap 0.1mm smaller than as they come out of the paper box. Makes the transition path shorter and the flame will last longer.
NGK/Bosch/ Super Spitfires/ Give 100 HP-extra plugs/ multi-electrodes : on a testbench (in a former life I have done it) it doesn't give a single bit of difference. You only get a nicer box with a sexier picture on it, real expensif ones give a sticker for the rear hatch, so that is very important.
In news: snipped-for-privacy@news.telenet.be, Tom De Moor wittered on forthwith;
Heh, Cheers Tom. The above has pretty much confirmed what I wanted to hear / suspected, and it's nice to be occasionally reminded that this NG isn't completely useless all the time.
Made exactly to plan (IRL the plans are copies of the originals, they are indeed blue).
Blueprinted engines are at max tolerances and are optimised in very way the figures on the plan allow and use only OEM parts.
There are companies specialised in blueprinted engines where some manufactures take their new engine (straight of assembly line), they rebuild it and find 10-20 % hidden power.
Nope: they ain't cheap.
Never wondered why the constructor sponsored car in a mono-make championship very often wins?
"Pete M" wrote in message news:f3npre$ta8$ snipped-for-privacy@registered.motzarella.org...
formatting link
I would suggest that being now a turbo motor, that the twin or preferably quad electrode 'un's are what you want, no doubt 1 or probably 2 grades colder than factory NA spec. Depends abit on what technology is responsible for generating the sparks now also...
Modern engines are built to tighter tolerances so there it a lot less to be gained. The main point was that the engine was to all intents and purposes a standard engine as it was still within the OEM tolerances just that it was all at the optimum end of the tollerences.
"Pete M" wrote in message news:f3npre$ta8$ snipped-for-privacy@registered.motzarella.org...
formatting link
Plugs are a gap between two bits of metal and you pass current between them. The only technology to change in them has been fancy metals hitting the mass market. Multi electrode or surface discharge don't provide better sparks but do last longer as the spark will take the path of least resistance and go to the closest point, as one electrode or part of the electrode erodes it will swap to the other.Multi electrode plugs do have the slight disadvantage that there is a larger electrode area that blocks the flame front where as surface discharge use the mounting ring as the electrode rather than having one hang over, this gives a full arc that discharges can happen across it's just the centre electrode that "wears" they also have nothing to stop the flame front from propagating and as they don't have the overhang they are ideal for high compression engines (not that you have that problem) as they don't extend into the engine as far. Unless there is evidence of preignition, detonation or that the engine is running hot (white eroded electrodes) then they are probably of the correct temperature range.
So the marketing boys of all constructors claim. The reality is...
Which when done correctely gives a minimum of 10% extra HP and in most cases around 20%. Yesterday, today and tomorrow.
The reason for this: no constructor will make an engine on the outside of tolerances nor will he correct errors induced by mass production if those errors are not detectable in the normal operational range.
Just to give an idea of the "very tight tolerances": on a high output engine of a certain German constructor we found differances in piston weight of 3 grams.
Manuals were checked: differances up to 4 gr were deemed acceptable. I am not talking about a cheap, everyday engine in a cheap everyday car but a engine for which 1 piston is invoiced the nice sum of 400 Eur + VAT and it is a V8...
That if you have ever striped a new Toyota engine it's the truth. You will be lucky to get an extra 3% from blueprinting a modern lump. Companies that do blueprinting will tell you different but they would.
We have had a Yaris cup in Belgium, it raced the standard engine vvt-i.=20 Strangely enough the standard (iirc 131 HP-engine) on which only the=20 plugs, airfilter and muffler were free, was from the first race around=20
180 HP for the top ten. They lapped the rest of the field after 15=20 minutes. By the second race all engines were "recondioned" by a certain=20 company and all were within the rules of standard engine.
Renault had experienced the same the previous years and counteracted by=20 handing the car's ECU out by lottery before the race. Still of the=20 season it were -on the exception of one race- always the same engines in=20 the top five. =20
No constructor will go to the outside of tolerances on bore, on=20 crankshaft, on pistons because if he does so his engine can not be=20 reconditioned. No constructor will produce a rattling engine because the=20 piston-bore clearance is at its max.=20
Further I have still to see the first standard engine in which the head=20 was flowed, in which the valve inserts were as on the plans, in which=20 the inlet path was smooth all the way, in which pistons within 1 gram of=20 weight. I never have (even on bike engines) have valves where the valve=20 contact area was on the outside of the valve diameter and 0.7 mm wide.
On the other side the blueprinted competition engines I had the above=20 without exception, 10% extra power is very conservatif and will be=20 obtained without a full blueprint of the engine.
The blueprinters dream is an engine made in millions, for a long time,=20 for applications in several models all over the world like for example=20 the Citroen 2cv -engine: we build a fair lot of them and from the 32 HP=20 at the crank (very optimisticly claimed by the factory) ww obtained 65HP=20 (=B12HP), using only OEM-parts, handpicked, carefully modified as per plan= =20 and optimalised. Cost of such an engine was more than a complete 2cv=20 new.
On modern engines a "flower" will allready obtain a result higher than=20
10%. The cost of 2kUKP for a flowing a 16V-head is justified just like=20 there are sound reasons why very low badges of high outjut engines are=20 assembled by hand.
Go and compare bike engines to car engines: you will enter a another=20 world if tolerances and finish are concerned. Even on bike engines the=20 above still is real.
Modern engines are better build than before, their control systems not=20 as easy because everyone uses his own electronics but at the mechanical=20 side of things the possibility of improvement are still very much there,=20 maybe even more because oil and fuel are better controled and known than=20 they ever were.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.