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G'day,

Straight to the point. Bigger is better (for oil return).. but Speedflow suggested I go for a M20x1.5 drill and tap of the sump. Is this too extreme? #structuralintegrityaffected?

I'll be going from a -8 from the tubby, to a -10 line

Also, could I just use hair wax/gel when I drill to try to grab all the shavings? All good hairdressers have that

TIA

Paul

Hey Paul,

When in doubt, check what OEMs do. They have bigger R&D budgets than you and I.

The return sounds pretty large, but I did note on my SP that the oil return is around that sort of size. Instead of tapping the sump, the fitting slips in and tightens down using an external nut over the fitting. Requires RTV for sealing.

I don't think drilling a large oil return hole is going to affect the structural integrity of your sump. It's not exactly a load bearing component (unless you rest the engine on it out of the car etc).

Sounds like you're doing this with the sump on the engine - it's an accepted procedure, just be careful not to put the drill in too deep (use one of those fancy stepper bits from Bunnings etc) as the oil pickup tube will be right behind where you're drilling. Also, you want a round hole, so again, don't use a drill bit.

Lastly, Google procedures for picking up swarf during the process. Pick one that you're comfortable with that makes sense to you. Once complete, change oil and filter (and maybe again after running the engine for 5 min if you're that worried about it), and you should be fine.

Lastly lastly, search forum for NitroDann's thread about turbocharging your MX-5 for $2000 - he has a procedure of how he performs a sump tap in it IIRC.

Thanks for that- you second guessed many of my concerns!

I've got a progressively increasing 'cone' shaped drill bit that goes upto 20mm diameter. Hopefully that negates the risk of hitting the oil pickup.

I also just purchased a ($35) 20mm with a tapered thread (hopefully that fits the bill)

I'll use plenty of grease- I guess the question was whether hair wax is sufficient, tongue in cheek but semi-serious.

I've seen the FM guide and Begi guide.. the revlimiter and nitrodann guides are golden too. Can't go wrong right?

Good luck. Take photos and write up in the how to section for the next person who tries?

Thanks mate.

Here's some pics:

Stepper from bunnings, screwdriver drill also from bunnings - $60 drill and $30 stepper
Initial drill- not straight, but easily correctable when you gain more real estate by going deeper


A massive amount of shavings:


You can see how deep I went - in this precise position I was 'lucky' that I didn't seem to have hit anything in the sump, based on my post drill finger exploration:


Tapping, with a tapered tap.. so didn't quite hit 20mm diameter with the drill, leaving the work to the tap to ensure a snug fit


Finished product: I've never done anything like this before, so fairly happy.

Thanks for details, what turbo are you using and any chance you could post up part numbers of pieces you used? Did you use jb weld on the threads at all?

Good question - so the supplier for all good quality oil lines/hoses is speedflow. I did use a silicone sealant.

They have local suppliers throughout OZ, I suggest phoning speedflow (the helpline is really good).

This is for a Greddy TD05-16g. Return line has a 'plate', so i got the plate and associated parts:

For return I used a MASSIVE -10 line. On the sump I used M20x1.5 (BIG)
Parts:
-463-01 - Adaptor for turbo return. 38mm-44mm hole centre length -8 female
-920-10-08 - -8 into -10 size
-T200-10 - -10 teflon hose. needs to be approx 6" (THIS IS TOO LONG)
-201-10 - STRAIGHT HOSE ENDS -10
- 735-10 - -10 M20 x 1.50
Drill and tap M20x1.5

Now the biggest downfall is the hoses arrived UNASSEMBLED.. which meant having to find a place that creates hoses- good luck with that. Consider find this out first, because they may be able to sell you a complete hose with everything you need.

Pirtek should also be able to provide hoses and fittings


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I used a 3/8" bspt fitting with a 5/8" nipple. i used a blue goodyear 5/8" hose. its bloody good. been on for 8 years and still perfect.

When we drilled our sump for the oil return, (with oil still in it) we slanted the engine (out of car) to get the drain plug low, then drained the oil, then poured a couple of litres of kero into the turbo oil return hole as fast as we could to flush more swarf out - seemed to work well. After it was running we got it hot a couple of times and drained the initial oil fill out again.
jp

Good stories, thanks for sharing.

I flushed with mineral spirits, left it overnight then filled with oil.

Call me crazy (.. and here's my number) but i didn't change the oil filter. I left it 5k before my next oil and filter change.

Pleased to see no shavings in the sump drain.

Apparently.. aluminium 'burns up' in the combustion chamber.. but don't quote me on that. Generally happy- this has to be the second hardest part of a turbo install after economically justifying it to your wife/girlfriend/mates.