So i've been wrenching now for about 27 years,mostly VW's but also everything else and then worked at a couple of vw dealers for a total of 21 years , and have worked on my share of diesel [lots here in Quebec].
However the hi-po diesel scene is new to me, and i've never done anything other than routine maintaince and repairs. Got the bug though when i chipped and nozzled my injectors in my 98 TDI. My question is: i always thought that the rev limit was a function of trying to keep the valves from hitting the pistons and that a diesel was also limited by breathing. All of a sudden i see some guys talking about 5500 and 6000 redlines! If the pump governor is modified, what is the limit? or will it stop breathing and self govern? Have i mentioned what an amazing site this is; i'm becoming as addicted to this one as much as The Samba
the moving parts weigh more, so it does put more strain on everything. i've heard that the TDI's don't like to rev so high, but that is an issue with the pump. i think PD engines can rev quite high due to the fact that they use a single unit injector for each cylinder fired by the camshaft. so as long as you use an oil that can take the beating from that, it should rev pretty good.
Giles can make a pretty mean pump that can rev pretty high
the governor is set to limit the fuel to protect the engine, and also keep the engine inside of its peak power. diesels don't many much if any torque past 4000 rpm. by then its all just HP.
does the computer govern the engine, or does even the TDI engine have the governor assembly as found in IDI models? if it is all computer controlled then there shouldn't be a problem upping it like that. the only issue is internal parts breaking from all the extreme internal pressures (the piston and head on the pump... Tintin was able to break a TDI pump with a 12mm head!! i think he revved past 4500 with it)
diesels are limited by breathing, so that is something to consider... larger downpipe and nice big intake. a bigger turbo flowing more air is also a good idea.
so then what is the safe rev limit for a 1.6 or in my case a late 1.7 l na ?
besides the governor limiting the fuel? Last week when i was getting out of snow bank [fresh snow on ice, why oh why didn't i get my Nokian happi's studded?] i was spinning the thing up past 5000 rpms and was a little concerned.
problems when you go that high in the rpm range are more to do with oil consumption and blowby. if you can get it up to and or past 8-9k rpm then there will be some destruction though.. do a search for Jake's over-revved head. accidently put it in 1st when he meant for 3rd... his head got fried! i'm wondering if it was actually the spring rate that allowed the valves to stay open long enough to be slapped by pistons... :?:
always use a good synthetic oil though, and that should help your engine last longer if you like the high rpm's
Look up the Giles pump video where he runs a pump waaay up the rpm scale.