I know the VR6 is already a pretty robust engine. but if you were doing a rebuild, what would you do to increase power while either increasing or (at least) maintaining reliability/longevity?
Big valve head, Schrick manifold and 263 cams. With a decent exhaust and remap by someone like Stealth this will see around 220bhp without any need for internal upgrades. If going boosted then bolts can be upgraded to ARP. If going silly power then Rods and pistons but we are talking well over 400bhp. My VRT runs around 380-400 and only uses ARP bolts without issue, even when I had the boost turned up to 24psi by mistake due to a split hose to the gauge causing it to under read. Normally runs around 17psi. Gearboxes become the weak link on high power cars, as I found out whilst running the boost too high. lol
If I was going FI it would be with a supercharger. I know it wont get me the $/hp of a turbo, but I don't need crazy numbers and I prefer a linear power band (as well as preferring bottom end to top end). at this point im 50/50 on doing this and with the build I have planned I don't feel that it would be a problem to add this later. im I just got a 98 12v vr6 with a bottom end tick to play with. my plan was to rebuild/blueprint and use 268 cams, HD springs, lightweight lifters and a CAI. I would run a 2.5" exhaust and software to match. big valves/exhaust porting is possible, but a bit out of my depth. Like I said though, my goal more for endurance than power, this car is going to be abused. The car already has a stock VR in it so Im in no rush and have no need to cut corners. the other part of the plan is a dry sump conversion with an oil cooler. I have a friend with a fetish for overbuilt oiling systems that is speccing a kit right now. the goal is that in addition to solid, consistent oiling i will be able to relocate the tank further back (likely behind the passenger seat) and take some of that weight out of the front end then actually lower the engine a bit as well. I guess my real question is, what are the weak points in the VR and how would you overcome them?
Considering the VR's design phase would serve you well mate, they're solid motors I've spent a little time with my hands in the guts of a few quick ones. Generally the N/A ones were left stock, cams and mapping and the usual bolt ons won't even make them blink, I'd generally want to refresh an engine to original specs these days though with the age of them but even that is probably excessive. When they were N/A but making real power - Bored, ITB's, head work with a valve job, lairy cams etc and really needed to last a couple of seasons - on top of the aforementioned stuff they got forged rods, pistons (although that was probably as much about upsizing as it was strength) and ARP bolts throughout. Please bare in mind it's pretty much 10 and I'm knackered so please don't take that as an exhaustive list, that's just all that springs to mind. Still OEM bearings used, never saw ACL or similar harder "race" bearings come into the mix, just to throw that in there. With FI there seem to be so many people simply throwing a handful of ARP bolts at them, if they even bother with them, and making serious power I totally agree with mk1 valver I'd go for rods and pistons just because I'm paranoid, but I'm sure a head spacer and buttoning it up with ARP's and you'd be golden... unless you've been watching too many European VRT videos Just personal observations and thoughts of course so take with a pinch of salt.
A known weak point is cylinder 1 on the 2.9 blocks due to thinner walls. Not a hugely common problem to the point that you HAVE to worry about it but if going FI then a 2.8 block would be a better starting point given the choice. If thinking about superchargers then make sure you do your homework. Have read a few stories of people being very disappointed with theirs and eventually changing over to turbo due to a complete lack of low down which is what the SC is meant to be good at. Rotex may be the one to go for and avoid the likes of VF but having never run SC can't really comment. Having run mine for some time I would actually prefer a really well set up NA VR now. Too much power through a FWD becomes a real chore and you lose a lot of the fun of working the engine through the power band whilst in the twisties. The only real weak points of the VR are oil temps and it sounds like you have that covered. EDIT; agree with Tom about standard bearings and head spacers for fI. These engine are pretty bullet proof.
thats my main reason for doing this. 800whp is ungodly cool and impressive, but in a fwd street+ application it would just be a pain. I would much rather spend my time and money on an engine that makes solid power but can withstand hard engine braking and sustained high rpm cornering. Like i said, superchager is a thing to consider but not really a goal. If I fell backwards into a eaton or vortech I wouldnt say no So it sounds like my list is pretty complete (adding int the ARP bolts).
BTW, if anyone has any articles on cam discussion or engine building in general I would appreciate it! searching the forum has been a wealth of knowledge but I know theres more out there!
Disagree with tom.rich's comments about N/A VR6s. Mine was a VERY high mileage (160k!) 2.8 post 95 engine (M3.8.1) (known as OBD II) that was freshened up with all new cam chains/guides etc Sharan AMY head gasket for slightly raised CR (10.5:1) Dougherty racing 268 cams Unorthodox alloy flywheel CAI and usual 2.5" 2 box exhaust, eBay tubular header. Chipped by United Motorsport, 7200rpm limiter, raised speed limiter etc. Was 205-216hp depending on dyno. Went and sounded very well for what it cost to do. Would have been nice to add to the above spec MORE compression (in the 12s), big valve head, and head work, lightened crank etc etc but those cost money and tbh, you might as well fit a 24v that flows better for a start.
Apologies in advance, not trying to be a cock even though it always comes across that way on the internet... From what you wrote, yours had cams and a chip and the usual bolt ons, so a lick over 200, almost identical to what I mentioned, and you did almost exactly as I said along with it - a "freshen up" with OEM bits I've no objection in the slightest to disagreement, just a little curious which bit you were disagreeing with? More for my learning than anything else, not a dig in any way, shape or form I've seen a couple of N/A ones go pop even with the full compliment of goodies I wrote above, case in point this one I pulled last year, forged pistons and rods, ARP throughout, admittedly high comp and very good power of course, but as said personal observations have made me a bit paranoid but I've no doubt at all that VR's are absolutely fine stock and I know they're proven to be by folks like yourself
Maybe I miss-understood this sentence then. Did you mean the internals (bottom end) were left stock as the bottom end is robust?? I read it as you were saying that it's a waste of time adding the usual bolt ons as doesn't gain anything.. If so I apologise!
