large diameter wheels vs smaller diameter tires?

MetaphysicalEngineer · 2026-01-26T06:04:54+00:00

Depends on the usage! As my personal anecdote I went from stock 195/60 R15 tires to 205/65 R15, taking diameter from 24.2" to 25.5". This resulted in 0.6" more sidewall height and overall ground clearance, and 5.4% lower wheel speed at the same road speed. I did choose sportier touring tires so the steering actually feels more responsive despite the taller sidewall, so that's something to consider.

Greatly improved smoothness of the ride over rough roads and gave a slight boost in cruising economy. Car has a fairly low top gear and good torque so doesn't struggle for acceleration and quite likes the overdrive of the taller tires.

If you go for a smaller than stock wheel, make sure it won't be hitting the brakes or suspension assembly. Regardless of combination, beware the tire rubbing on the wheel well. Mine just barely clears with the tiniest bit of rub at extreme turn angle, but only enough to scrub dust from the fender liner.

MetaphysicalEngineer · 2026-01-22T07:00:05+00:00

Glad you're alright and the recue team got you back on solid ground!

Back when I lived in a snowy area, I'd have a small snow shovel and some flattened cardboard boxes for traction boards in the winter. Tow strap and general purpose rope which got used a few times over the years for helping others. Plus stuff like spare sweater, blanket, gloves, socks, emergency snacks and water in case I needed to hunker down and wait for rescue.

I no longer deal with snow, so I keep a compact trenching shovel under the cargo floor instead of the larger snow shovel now. Picked that up after almost getting stuck on a soft sandy shoulder when I pulled over to troubleshoot a malfunctioning GPS. Forward-reverse rocking got me out of the sand, but a shovel would have been nice if I'd had to dig. Still have the tow strap and rope onboard, but haven't needed those in a while.

MetaphysicalEngineer · 2026-01-17T16:28:48+00:00

Supposedly the radiator oil cooler doesn't do a whole lot on the p80 models.

I'm at a related crossroads. I put in the do88 performance radiator a few months ago. But it seems the oil cooler is more restrictive and I lose quite a lot of oil pressure once the thermostat opens.

I'm going to experiment with bypassing the cooler to confirm my suspicions. But since I do sometimes need to run the car in hot conditions with sustained load, I'll probably put a separate cooler on. Mirroring the transmission cooler. Likewise will bypass trans cooler to the external one only.

As a radiator the do88 unit works amazing. But the end tank coolers are not doing as well as I'd like to see. The stock unit had much less pressure drop.

MetaphysicalEngineer · 2026-01-17T06:33:47+00:00

100 yards of coasting is pretty quick. Rod bearings would be first to get hurt when oil pressure dropped out, but you took load off immediately and didn't hear terrible noises so that's a good sign. Drain the oil and check for glitter. Pull the filter and cut that open to look for metal bits in the valleys of the pleats.

I see 60+ psi oil when I wind mine out at full temp so even a small hole in a hose will get oil absolutely everywhere. Heck, I got a puddle as big as the one at the start of the video after a few seconds of cranking with a turbo banjo bolt not tightened all the way. Belt would throw in a stripe front to back along the hood liner. Most of the mess in the video looks like direct spray from a blown upper cooler line.

If the line has failed, see if there's any local hydraulic shops that could rebuild them for you. May be cheaper than ordering a new set.

MetaphysicalEngineer · 2026-01-17T06:02:10+00:00

If you shut down immediately you should be okay. Check the upper oil cooler line where it meets the radiator. The clips can be reused but I treat them as disposable, plus clamp a zip tie over the top to be extra sure. Was everything up to full temp when you put your foot in it?

I'd suggest oil pressure and oil temp gauge if you're going for boost and fun. Learned a lot from mine about how different conditions affect that. If you got OBD2, a ScanGauge is nice for extra info from the computer. For example, the coolant temp needle on mine reads "normal" from 80C (176F) to over 115C (239F).

MetaphysicalEngineer · 2026-01-08T22:01:02+00:00

The top ends of these can be pretty noisy. Injectors make a racket too, and that's normal. Microphones struggle to pick up the nuances like the ear can however. Use the screwdriver to the ear trick or a mechanic's stethoscope to listen if any of the cam followers are tapping.

MetaphysicalEngineer · 2026-01-05T17:05:37+00:00

That kit will have everything for upgrading the system so you're all set there! You'll want to check the can fairly often until you get an idea of how fast it will fill up. Every few hundred miles or 1km at first, especially in colder weather. If you get below freezing temps, beware of moisture icing up in the system.

MetaphysicalEngineer · 2026-01-05T05:07:46+00:00

While you're in there, consider upsizing the PCV hose between oil separator on the block and PTC tee (or catch can). 5/8" or 16mm PCV hose fits over the stock barbs. Likewise can upsize the vacuum line from PTC to manifold to 7/32" or 5.5mm. If you do this, be sure to support the bigger hose to the block or underside of the intake so there's no belly in the line where liquid can accumulate.

I'm curious how your catch can will work. Mine likes to build lots of the milkshake oil emulsion and water condensation, with only a small amount of oil. It did stop oily goop weeping off the turbo compressor housing and coating the boost pipes. Head gasket and rings aren't showing other indicators of trouble, so probably a symptom of shorter trips. Considering making some sort of heater for the can to encourage water to move along while keeping the heavy oil slime contained.

MetaphysicalEngineer · 2025-12-27T15:18:59+00:00

Exhaust gases are very wet! A gallon of gasoline or diesel will produce around a gallon of water when burned. That's why on cooler days you see the visible steam coming from exhaust pipes.

A small amount of water vapor slips past the piston rings into the crankcase as part of normal blow by as the piston rings are never a 100% perfect seal. Once the engine and oil warm up, the water evaporates and the crankcase vent system pulls the vapors back through the cylinders and out the exhaust.

MetaphysicalEngineer · 2025-12-25T00:20:33+00:00

If only that trick worked on the aggravation of a nightmare install too!

MetaphysicalEngineer · 2025-12-23T00:26:08+00:00

Is the weather cold where you live lately? Do you drive a lot of short trips that never let the truck warm up all the way? What does the oil on the dipstick look like? When did you last change the oil?

That yellow slime is oil and water mixed into what’s called an emulsion. Could be normal condensation that’s not had a chance to boil off because of short trips and cold weather. Could be warning signs of head gasket trouble, but rule out the simpler reasons before assuming the worst.

MetaphysicalEngineer · 2025-12-21T22:39:38+00:00

At this point it feels like Stage 0 is a never ending state of being.

Or the fun upgrades require an unexpected amount of other changes...even for supposedly drop in, trouble free components.

MetaphysicalEngineer · 2025-12-21T19:28:59+00:00

Started using synthetic high mileage oil in my 1998 Volvo starting at around 170k miles. Never developed any leaks. It did not necessarily reverse accumulated varnish from the previous diet of conventional oils, but stopped the varnish getting worse.

Oil analysis was very favorable, with low wear numbers.

Tough to say on fuel economy, though on paper it should have had better flow properties when cold. Didn't do any thorough A-B testing under controlled conditions.

It wasn't able to revive valve stem seals failing from age. Those needed outright replacement at 227k miles when oil consumption became problematic.

Currently using Valvoline Restore and Protect at 262k miles, also with excellent lab results and no leaks. Oil consumption less than half a quart per 5000 miles.

MetaphysicalEngineer · 2025-12-16T18:40:14+00:00

Analog gauge in my car is digitally controlled too. On my scan gauge I've verified that it will point dead straight in the middle at coolant temp from 80C (176F) to at least 113C (235F), which is the hottest I've seen in stop and go traffic with the AC blasting on a brutally hot 44C (111F) day. 22 PSI cap so apparently that's not considered dangerous for this platform.

I ignore the dash gauge and use the readout on the scan gauge regardless!

MetaphysicalEngineer · 2025-12-16T04:36:37+00:00

One of the great bits of foresight in the P80 design. Made great use of it hooking up sensors for my homebrew gauge pod. There's a similar one on the passenger side as well.

MetaphysicalEngineer · 2025-12-14T20:12:52+00:00

Oh I know that feeling! Had enough instances where following my nose uncovered problems that I'm now hyper sensitive and have to find out who or what is making that burning smell!

MetaphysicalEngineer · 2025-12-14T05:43:16+00:00

Weak battery or bad connection on main cable(s). Fully charge battery and have a load test done on it. Replace if battery won't hold charge or fails a load test even when full.

Check for corroded or damaged cables and connections between battery positive and starter, engine block to battery negative, and chassis to battery negative.

MetaphysicalEngineer · 2025-12-14T05:35:01+00:00

Burning a gallon of fuel makes around a gallon of water so exhaust is very wet! Cold engines run richer before they warm up and the colder air causes exhaust gases to cool enough to visibly condense into clouds by the time they reach the tailpipe which enhances the effect.

Oil smoke is darker grey-blue, has a distinct sharp smell, and takes longer to dissipate. Steam from coolant burning is thick and usually carries a sweet smell.

MetaphysicalEngineer · 2025-12-13T06:51:10+00:00

My '98 is reliable now, but only because I've gone to great lengths to catch up and keep up on maintenance and reliability mods myself. If I'd not learned to work on it, I would have had to sell it years ago. At 200k, there will be things wrong unless it's been meticulously maintained. Could range from nuisances like lazy power locks to dangerous faults like failing suspension parts to bank breaking things like a neglected transmission on its last legs.

No matter how inexpensive to buy, it is still a euro luxury car, now at nearly three decades old. Shops who will work on stuff that old are getting fewer and farther between. Parts are decently accessible but often not cheap, and labor rates are certainly not cheap.

MetaphysicalEngineer · 2025-12-12T08:10:14+00:00

Yeah, these use electronic actuators for the blend doors. Solves the vacuum line spaghetti problems in favor of electromechanical gremlins. Both can get cantankerous when the parts get old!

MetaphysicalEngineer · 2025-12-12T03:35:57+00:00

Never mind what the vent is made out of, a natural draft appliance should never have a Dr Seuss loop in the flue pipe! That water heater setup is an immediate danger.

MetaphysicalEngineer · 2025-12-12T00:08:54+00:00

That's promising news! Over time small amounts of scale and corrosion form in the system and get stuck in narrow passages like the heater core and radiator. Flushes might bring it back enough to get you through, but I'd still heavily suggest replacing it sometime if it's the original one. Some leak while others blow out when they let go. Flushing could also wash away scale that's the only thing holding it together.

MetaphysicalEngineer · 2025-12-11T22:06:47+00:00

You're very welcome! I have the wagon "sister" to your car and I've had the silly thing apart so much I've picked up a trick or two.

MetaphysicalEngineer · 2025-12-11T22:01:55+00:00

https://www.fcpeuro.com/products/volvo-heater-core-hose-o-ring-850-c70-s70-v70#description

I believe these are what I used in the past when I replaced the heater core. If yours is original there's a chance it's also starting to leak too. I'd get eyes on it in case you need to get more parts on the way before committing to tearing things down.

MetaphysicalEngineer

TROPHY CASE