GT3 Oil Pump vs. Auto Verdi

[Evan Fullerton]

I'm starting to gather up parts for my engine build and I'm wondering if anyone has any experience good or bad with the 3 stage Auto Verdi oil pumps. With the continual price increase of GT3 oil pumps, the gap in price to an Auto Verdi is shrinking. If the Auto Verdi performs as advertised and is worth a few HP in reduced friction and increased scavenging with no increase in service requirements, I might in my twisted mind be able to justify one.

Anyone have an experience with one or hazard a guess as to it lasting hundreds of racing hours or 100k+ street miles like the GT3 pumps will go without issue? The Auto Verdi being a roots style pump with teflon coated lobes has me wondering if it is a 100 hour service, race only item, or something dumb guys like me would consider for their hot rod street/track cars that hopefully won't get torn down more then once every 200+ track hours and 50k+ miles.

[Flieger]

Never heard of it but if the teflon wears away aren't you basicaly just left with a normal gear pump? Or are the lobes twisted into a helix so there's more sliding friction?

[Evan Fullerton]

Max,
It's basically a NASCAR oil pump adapted to directly replace (with some case clearancing) a GT3 pump. They are made in Sweden and supposed to be the shiznit for V8 applications but I don't know anyone who has used their Porsche application. We talked to the sales rep about them when I was playing with Cup cars before I got a real job but never got past the "that's cool" part as PMNA was doing the rebuilds for the cars I worked on. I believe the pump lobes are aluminum under the teflon coating and they are known for really tight housing tolerances.

You can see the Porsche pump here
https://www.youtube.com/watch?v=HfMaGaYuDTk
About Auto Verdi

[chris_seven]

It is interesting to compare the two basic designs and the benefits they seem to offer and both gerotor and gear pumps have their supporters.

On the pressure side most pumps are capable of delivering adequate flow to the bearings of an engine and depending on the restrictions in the system the greater the flow capability of the pump the higher the pressure that will be developed.

The pressure relief valve generally protects the engine from excessive pressure but the greater the flow capability of the pump the more oil that will flow through the pressure relief valve (PRV).

In conventional hydraulic pumps terms by-passing significant flow through a PRV is undesirable as some heating of the oil is caused by this action. It is quite difficult to measure this temperature increase in an engine oil pump but it would be customary to select both components to optimise their behaviour in this respect.

The gerotor pump can also have a relatively 'spikey' output depending on the number of lobes - some GE pumps for example have 9 lobes and are reasonably smooth but in general 2/3 lobe pumps will produce a very different pressure/time output than a typical Porsche gear pump.

The Scavenge section of a pump is subtly different and improved sealing will generally result in lower crankcase pressures.

By running vacuum in a crankcase parasitic windage losses can be reduced and this must be a benefit in terms of both horsepower and oil temperature, the issue will be quantifying the difference.

The final consideration must be the ability of a pump to deal with debris and contamination in the oil.

I generally believe that gear pumps will tolerate more debris then gerotor pumps due to the cavity at the tip of the gears.

With a gerorotor pump the tighter the tolerance the more easily they can block.

Clearly this is not much of an issue in a well maintained race motor that is routinely re-built but could be an issue when fitting a very close tolerance pump in a road car and not paying quite so much attention to oil changes.

[Evan Fullerton]

Chris, I always enjoy reading your take on things. Pretty much goes with what I was thinking, GT3 pump is a known quantity that works well, the tradeoffs for possibly 5hp likely aren't worth it for my usage.

Now to decide between straight cut steel intermediate shaft gears or a steel helical cut.

[Fly911]

I'm in the process of rebuilding my '87 3.2L, and I chose the GT3 pump (along with a lot of other GT3 parts) because it fits (with some crank case machining), and it's well proven and bullet proof technology. Even if it should be $500 more expensive than the other pump, that is in my case a 1% difference in parts cost. The oil pump is a too vital part of the engine to experiment with, and even if it was for free, I wouldn't have done it!

[Jeff Alton]

50k in parts, love to hear the specs of your 3.2.

Cheers

[SexOnTheBeach]

Originally Posted by Evan Fullerton

Chris, I always enjoy reading your take on things. Pretty much goes with what I was thinking, GT3 pump is a known quantity that works well, the tradeoffs for possibly 5hp likely aren't worth it for my usage.

Now to decide between straight cut steel intermediate shaft gears or a steel helical cut.

Been using the straight cut gears from JB racing in all my high hp builds, all without any problems whatsoever, cheers.

[Fly911]

Jeff Alton, here are the mods for my 3.2:

997 GT3 crank, knife edged, cross drilled and balanced
997 GT3 Pankl titanium rods, all weighted and balanced (with stronger ARP bolts)
997 GT3 oil pump
997 GT3 Cup intermediate shaft and gears
102mm LN Engineering NiCaSil cylinders
102mm LN Engineering special light weight pistons with titanium wrist pins (balanced to +/- 0.1 grams)
Engine case spigots bored for the bigger cylinders, machined for the oil pump and internals boat tailed
Cylinder heads machined for twin plugs, intake and exhaust ports bigger and polished.
993 RSR valves, 52.5mm inlet and 44mm exhaust, titanium retainers and race double springs
Combustion chamber and exhaust port ceramic coated
Piston tops ceramic coated
Elgin race camshafts, 325 degrees inlet, 318 degrees exhaust (I can't remember the lift)
Pauter racing valve rocker arms
Fabspeed stainless steel equal length headers (42mm ID)
997 GT3 4.0L titanium muffler with center exhaust
Canems ECU that will be dyno tuned
Jenvey 48mm ITB's

This is probably as far as you can stretch a naturally aspirated Carrera engine...

Gear Box:

Lower 3-4-5 gears from Guards Transmission
Steel shifter forks and synchros
GT limited slip diff.

The parts sum up to around $45k to $50k, plus the labor. I realize that I can get a well equipped 981 Boxster for that amount of money, but that is not the point (I already have a Boxster...). The point is to have a matching numbers car that on the outside looks 100% original, but with suspension and brakes that match the engine power, and gear box that keeps the revs up in the sky...!!!

[Tippy]

Originally Posted by SexOnTheBeach

Been using the straight cut gears from JB racing in all my high hp builds, all without any problems whatsoever, cheers.

Would love to hear the sound of the straight cut gears.

[911 tweaks]

I would love to hear ANYTHING on this engine and car build for that matter... awesome... thx for sharing...

[KTL]

Can get the straight cut intermediate shaft gears from Pauter too. Quite a bit cheaper as well.

[KTL]

Here's some pictures of the Auto Verdi pump

Auto Verdi Pro Series 3-Stage Billet GT3 Oil Pump (30mm) - Auto Verdi - Products LN Engineering

[Fly911]

WOW! The Auto Verdi pump is $2,600, I paid $1,700 for my OEM GT3 pump, new in box!
Go figure...

[Tippy]

Hmmm, NASCAR engines are one time use, right? Different than our engines.

[Evan Fullerton]

They rebuild NASCAR engines and the parts get filtered down the ranks before they fully time them out. A JE piston engineer I was talking to one time said that after one of the big names runs a race, those same piston rings will wind up in 2 or 3 other engines with other teams before they discard them.

Our oil pumps not being serviceable without completely tearing down the motor has been what has steered me towards the known service life GT3 pump but it's hard to turn down HP without increasing the stress level of the engine if there was experience with the Auto Verdi pump going the distance.

[chris_seven]

It would be interesting to know where the HP increase in using the Auto Verdi pump arises.

There are two main areas that could be considered.

The first is that the general windage of the rotating assembly reducing due to improved scavenge.

Windage of a disc is a function of the viscosity of the fluid it runs in and the speed of rotation.

It's relationship with viscosity is broadly linear but its relationship with rpm is proportional to the 3rd power and below certain critical speeds can be considered as insignificant.

On a high rpm NASCAR engine running at peak rpm for much of its duty cycle a HP saving translates to an improvement in top speed.

At normal engines speeds benefits may be marginal so the duty cycle of the engine is part of the decision matrix.

Unhappily there never seems to be any published data so the judgements we make are usually subjective.

Measuring the suction pressure vs rpm of the two pumps would be a good guide to this area of the pumps performance.

The other source of parasitic loss may be gear windage. This is similar to disc windage but the math is subtly different and at high speed can be significant.

At pitch line speeds of around 125ms^-1 losses generally become significant and the way to reduce losses of this type is by shrouding the gears.

The design of the pump body performs this function very effectively so losses due to gear windage are already at a minimum.

Having been involved in the design and manufacture of gear windage test rigs for several years I would estimate the losses of a pair of closely shrouded gears would be at worst about 0.5% of the driving power.

How these losses compare with a close tolerance gerotor pump is very hard to say without a sophisticated test rig and accurate torque and speed measurement but it would be fascinating to see some data.

I had a close look at the Auto Verdi pumps at the recent Autosport International show in Birmingham. They seem very well made and if construction quality was the only factor I would buy one.

I am very interested in the Ti wrist pins and would like to know what coating has been applied.

[chris_seven]

Originally Posted by KTL

Can get the straight cut intermediate shaft gears from Pauter too. Quite a bit cheaper as well.

There seems to be two different shaft gears and it would be good to understand the difference.

I realise that there are 901 and 930 part numbers but have never paid much attention to the differences.

I would also be interested to know how these gears deal with the '0' and '1' size differences.

[KTL]

I haven't spoken with Pauter about how the straight cut gear set accounts for the different 0, 1 codes but I can ask. I have to order some rods in the near future.

Here's the details of the different gears in the spec book

[chris_seven]

I would guess that if they use an involute profile a spur gear will be moderately tolerant of centreline change - at least to the extent of the 0 and 1 differences.

I am not sure if the original helical gears are quite so tolerant of the centreline.

The difference in the two gears shown on Pauter's site is one has round holes and the other more oval slots and I don't know why.

Do you have any idea?