Twin Charging a Honda CRX 3

[patprimmer]

I having a moment of madness and considering twin charging a 1988 Aussie model CRX.

Aussie model has the DOHC D16A8 engine and factory A/C and P/S both of which I must retain.

The plan would involve a second hand Toyota SC14 roots type blower.

I already have a turbo being a brand new Garrett GT2859R-707160-9. M24 cast on compressor.
Ball bearing, water cooled bearings.
Compressor is 44.5 inducer, 59.4 exducer, 56 trim, 0.42 A/R
Turbine is 53.8 wheel dia, 62 trim, 0.64 A/R
It has an internal waste gate but I also have a 41mm Chinese external wastegate.

The turbo is correct size for my ambitions turbo only, but probably a bit small for twin charged.





Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[ivanheow]

a couple of things that maybe helpfull pat ,one is that ,after recently building a 1.4 gm motor turbo propane , i did a bit of research on lpg octane ,some of the info i turned up suggested that the octane varies a fair bit as the ratio of butane to probane varies ,and that in aus it can get much lower than 105 .

the other is that , if you run 250 bhp on the blower , how can a 260 bhp turbo add anything ?although ,without looking at the map , id expect a 45mm inlet to run around 310 bhp .its still not much of a gain ..i feel a bigger compressor ,and a much bigger turbine is needed .

remember ,as im sure you allready know ,your ex gas quantity is greatly increased by the blower .something in the 50mm comp inlet sort of size ,and a gt 30/35 size turbine maybe .

regards
robert

 

[Warpspeed]

70btdc,
Building exhaust turbine wheels that stand up just fine to the extreme EGTs experieneced in gasoline SI engines is not a problem.
But you are suggesting the exact same materials when used for the stationary vanes are not good enough?

I don't think so.
This is all way off topic, I suggest you start a new thread.

 

[70btdc]

Yes, exactly. The vanes themselves, the dowels that pin them. The wheel is given a much larger clearance tolerance to the housing. If the vanes had the same tolerance, the air would go right round them.

I'll post up some info in a new thread.

 

[1gibson]

Dodge Daytona, late 80's. 2.2l 4 cyl with VNT/VGT turbo.

A lot of the diesel turbos aren't going to last forever if you throw them on a gas engine, but that doesn't mean material limits are impossible to overcome.

 

[Warpspeed]

Reliability is NOT the problem.

Getting it to work at all is the problem.

Might I respectfully suggest that you have never yourself fitted one of these turbos onto a gasoline engine, and tried in vain (sic) to make it work.
Lots of other people, including myself have put enormous effort into it, and we have all very quickly discovered the same things.

And as a matter of interest it is never the vanes themselves that jam up as you seem to think. It is the circular sliding vane actuating ring that links all the vane toggles together. That jamming problem comes from gradual exhaust deposit buildup (mainly lead), it is definitely not a materials related or heat problem.

In diesels these deposits are oily, in a high mileage gasoline engine they are as hard as concrete.

Unleaded gasoline goes a long way to reducing hard exhaust deposit buildup, which is probably why Porsche have never suffered from well known jammed vane problem.

I know you don't believe me, but these VNT turbos have been around for over thirty years. Where are all the winning race cars using this variable vane technology?

 

[patprimmer]

Warpspeed

It has been about 10 years since leaded fuel was allowed in Aus except for aircraft and a very few special race events. Even the V8 Supercars use unleaded.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Warpspeed]

Very true Pat.
But the VNT turbo has been around on diesels for decades.

But twenty or thirty years ago, the hard very dry exhaust deposits usually eventually led to vane jamming problems in high mileage engines.

The Japanese have been pouring vast amounts of money into developing turbo production engines for a very long time, and not a single variable vane turbo anywhere to be found. Ask yourself why is that?

As a matter of interest the race winning Formula One Honda TAG turbo engines used a pair of VNT turbos. But then the required power band was very narrow.


The Honda engineers know all about variable vane technology.
But no variable vane production Honda road cars ever surfaced.
And those Honda engineers are far from stupid people.

 

[patprimmer]

Sorry I didn't mean to sound argumentative as I know nothing of variable vane turbo technology, I was just saying in case your data was no longer really valid.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[HRHtex]

Off the subject a little - but I was surprised to hear on the recent Bathurst broadcast that the cars run on 85% ethanol/15% unleaded.

 

[Warpspeed]

Pat, I built up and developed my very first twincharge system over fifteen years ago, and have helped many other people with successful twincharging projects since then.

After that, I then started looking around for another off beat challenge, and VNT technology sounded really exciting, so I had a go at that.
After eighteen months of totally wasted money and effort I gave it up, and bolted on a simple ball bearing turbo, which was far superior to the VNT in every single respect.

Everyone from Joe the Saturday night street racer, to massively funded serious professional R&D outfits like Honda and Garrett have had a go, and given up on it too.

Twincharging has the advantages of both supercharging and turbocharging, without the disadvantages of either.
It is a lot of work, but fairly straightforward and easy to set up, understand, and get going to perfection.

Over all these years I have never known anyone that started a twincharge project to either give up on it, or be less than totally ecstatic with the final results.

 

[patprimmer]

I think I am onto a second hand M90 of a V6 Commodore.About $300 to $400 probably. Don't know condition, but I can probably borrow it to measure up and even test before I buy it.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[PorschaTwin]

Is asn M90 not a little big for your Twincharge needs on a 1.8l (I think) engine? I was thinking of an M90 size for my 2.1l Twincharge but my hp goals are 750bhp.....

 

[Warpspeed]

Not that big, the displacement of the M90 is 1475cc per revolution, almost exactly the same as a Toyota SC14.
But it is a far more robust blower. They do look larger, and that may be a problem.

If driven at about crank speed, it will work fine, have plenty of top end airflow, and it will last forever.

If it is going to be mounted directly over the inlet ports without subsequent intercooling, it makes more sense to use a larger displacement blower that will add minimal extra heat and not be really struggling with volumetric efficiency at very high rotor rpm.

If a blower is remote mounted, with plenty of intercooling after the blower, you can use a smaller blower and push it much harder.

For example, the Americans commonly use 6/71 GM blowers with displacements of 411 CID per revolution on small block engines. That may look grossly excessive, but in practice it has proved to work well.

An M62 would probably be quite adequate, but M90s are far more readily available at sensible prices.

 

[patprimmer]

skip

Find me an M62 for less than A$500 in Sydney, that I can borrow until I fit it up and I will certainly use the slightly more compact design.

I went to Eatons site and the critical size difference was any a few mm bigger. Length is not critical. It is housing width and depth (depending on orientation of mounting) that matters.

This will depend largely on whether or not I can flip the drive snout, gear box and rotors over 180 deg to reverse rotation

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[izzmus]

Look at what Jackson Racing has done - they made M62 setups for the various D-series engines. I think they stepped up to an M90 for 1.8l and larger engines. Either way, they drove the blowers directly via belt, with no jackshaft, so the snout must be reversible. The only odd thing that I remember them doing was driving the supercharger via a double-sheaved alternator pulley, for packaging reasons. We have the master cylinder in the way here, I suspect that Honda put the battery in the way on your car.

The rotors cannot be flipped over in the housing, as the output is triangular to prevent backfeed through the blower.

My M62 is in the bottom box of a large pile of VW parts, else I'd see how modular the design really is. (It is ex-Buick 3800)

 

[patprimmer]

The Jackson kit was for an M45. Endyne did a very few kits for an M62 but it never really got to kit stage just enough bits and pieces as a starting point.

They where both for the SOHC d series. Mine is DOHC D series with moderately different manifold flanges.

What there is of the Endyne kit is much better design but virtually unobtainable. The Jackson kits while complete are easy to get but really are pretty much junk.

I agree that Jackson and Endyne probably just flipped over the drive, but I need to confirm that can be easily done without need to make patterns or one off billet parts

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[70btdc]

Warpspeed, I really did fit a GT15V onto a Triumph Daytona 600cc bike engine a few years ago. It worked, but control was limited to around 50% range of vane movement, and an additional wastegate was needed; like Porsche. I believe this was only due to the control being vacuum actuated and had excessive transport delay for the application.


I agree the root cause of the vanes jammming is the deposits, but did not consider that the gasoline deposits would be much more different than the diesel ones. I now work with the diesel engines and we use a cleaning cycle to rid the 'sweep' of the vanes and the control ring of soot buildup after the engine is switched off and everything is hot.

In operation, once the layer has built up, the only thing to clean it off is the action of the vanes. Because the gasoline ex temps are higher, the vanes/control ring are more prone to this effect due to the vanes expanding more than diesel. The vanes get stuck at one end of the ring travel, as they climb up the thicker part of the deposits. There does not seem to me to be a way around this for relaible production VNT on SI.

Can I ask, how did you control the VNT vanes in your application? It is very interesting.. Was it purely mechanical i.e. throttle pulls vanes closed and then boost opens them again?

By the way, was the Porsche turbo vane-ring style VNT or just nozzle/throat style?

I would also like to just say that I am greatful for your opinion on these things, and that I am also a twincharge convert ) (was even before seeing these pages). I have a small engined, twincharged car that is in continuous development that someday I did hope to install a VGT turbo onto... I think for the sprints and hillclimbs the deposits wont worry me too mach as I can always remove and clean it.

 

[Warpspeed]

The VNT turbo I ran was from a Nissan Patrol three litre diesel, purchased brand new as a spare part.
At the time (2001) it was the very first and only VNT turbo available in Australia.

This also used a vacuum actuator to operate the vanes.
That baffled me, and still does. Where on an un-throttled diesel does the vacuum come from to operate the vane control ?

The very first thing I did was toss the original Garrett vacuum actuator and fabricate own actuator from scratch.

This slowly evolved over about eighteen months of messing about, but ended up having two diaphragms one behind the other, on the same axis to control the vane lever.

After all these years the exact details escape me right at this moment.
But the basic idea was that a vacuum diaphragm was directly connected to the vane actuating push rod. A light spring forced the vanes totally closed, and the vanes were opened by manifold vacuum. This is exactly opposite to the original Garrett actuator.
At engine idle and very light throttle, the vanes were wide open. As you opened the throttle and manifold vacuum reduced, (for acceleration) the vanes would close. Full throttle gave fully closed vanes.

Now there was a second pressure diaphragm and spring arranged to operate from boost pressure. This was not rigidly connected to the actuation rod, but could push on the end of the actuation rod to open the vanes at full boost pressure.

So the vanes open under vacuum, close at full throttle, and open again at full boost. The control system itself worked reasonably well, but the engine was never happy with the extreme exhaust back pressures created.

It sounds great, slam the vanes shut at 1500 rpm and watch the boost pressure quickly rise, but that boost was nothing compared to the 80+ psi exhaust back pressures that mode of operation created.

The effect when you floored it was the engine would die completely for about two seconds, then there was a MASSIVE surge of acceleration.

At the top end, forcing all the exhaust through a very small turbine again caused huge back pressure, and very disappointing power.

It really needed a wastegate, but that was something I never got around to trying. The whole complex mess had horrible drivability, but I never had any vane jamming problems - ever.

It was all a huge step backwards from twincharging.
Whereas twincharging was successful beyond my wildest hopes, the variable vane VNT turbo installation on the same engine was truly awful in every single respect.

 

[70btdc]

Warpspeed. I had better results than that on my installation (which was engine dyno tested), even before the wastegate was installed. The wastegate was installed only like an exhaust manifold blow off valve, that would relieve pressure that would otherwise cause spikes, trimming peak pre-turbine exhaust pressure, especially on transients.

I found that the range of vane operation is critical, and using the end-stop of the vane control ring lever to tune max exh bp and transient response must be completed before any other setpoints. There was no way that I could have ever closed the vanes to the maximum point. If I did ever go too far on the bp and snap the vanes open (i.e. max bp), I had similar symptoms - a combustion instability followed by a runaway boost condition and eventually misfire stall. The key was in fast transient control, and using the wastegate for safety.

The gasoline engine needs fast airmass control as the lambda operating range is much narrower than the diesel...

May I ask which engine you used the 3.0 VGT on?

The vacuum on the diesel engines is taken from the vacuum pump. They all have this to power the brake booster. The vacuum is controlled by a PWM solenoid, which goes high duty to increase vacuum to give a high exh bp condition. This has the benefit of a fail-safe system.

 

[Warpspeed]

Yup, the vane limiting screw is rather like the throttle stop on a throttle body. The vanes can actually be closed right up, completely blocking all exhaust flow.

Where you set that closed vane travel limit is critical, but I could never discover a setting that the engine was entirely happy with. If you don't close the vanes sufficiently, you lose all the supposed advantages of VNT technology. If you DO try to close up the vanes, the exhaust back pressure climbs to values that create huge exhaust reversion and massive exhaust pumping losses.

The engine I had this fitted to was a Mazda B6T, 1.6 litres, four valves, the DOHC factory turbo engine. The VNT turbo came from a three litre diesel with a rated power of 150Kw, which was my fairly modest power goal on gasoline.