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Corsa Updates
Here's all of the changes/fixes that have been done to the Corsa now it is on the road.
Update 1 (01/12/08) - Intercooler
Intercooler fitted, the intercooler is from a late model Astra diesel with some odd bits of pipework to connect it all up.

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After fitting the intercooler the boost dropped from 1 bar to 0.8 bar max pressure, I have re-adjusted the boost controller to compensate and took the opportunity to increase the boost further so it is now running at 1.3 bar max pressure, the combination of the two things has given the performance a nice boost :-)

Total cost of modification 25
Update 2 (01/12/08) - Exhaust
I've been watching out for a performance exhaust system but the good quality ones are to expensive and they also appear to have silly tail pipes (3" diameter and bigger, probably as the corsa is bit of a chav car !!!)
Tried running the engine with the back box removed and there was no noticable difference in the exhaust noise so I decided to do a cheap modification that involved cutting open the backbox and removing the baffles, a complete larger diameter system with free flowing silencers would be a better option but not worth the money to me (as I'm tight), the exhaust only has a middle box now and it sounds the same as it did originally.

Not sure if its made any difference, maybe its my imagination but it does seem to rev smoother ?
Update 3 (03/01/09) - Boost Pressure/controller
I've never been completely happy with the 'ebay special' 20 boost controller that I was using, I had to return the first one as the adjustment did not work correctly and the replacement did not seem much better, under full throttle in 4th or 5th gear the boost use to drop off which made me think the controller was not working correctly.

I saw a higher quality 2nd hand boost controller for sale (Turbosmart Tee Boost) and snapped it up for 25 delivered, just looking/holding the two controller you can see the quality difference with the turbosmart one, anyway its now fitted and adjusted to 1.5 bar, any gear it hold the 1.5 bar rock steady which proved the cheapo ebay contoller was not working correctly (you get what you pay for I guess).
Update 4 (03/01/09) - Fuel Increase
Had a little bit of free time so I thought I'd have a play with the fuel as I still have no sign of smoke when accelerating.
Rather than messing with the max fuel screw I decided to try increasing the on boost fuel via the injection pump boost compensator, this involves rotating the diaphram and pin/shaft (make sure you mark it before turning so you can return it to the original postiton if needed).

I recall when removing the white ring that the original pin position was at its least fuel setting and that turning it 180 degrees would move it to the max fuel setting.

I turned it around 20 degrees and then 45 degrees clockwise (the pin is eccentric so I don't think it matters which way you turn it) and still have no smoke issues, the performance is another matter though as it has made a noticable difference in the power (especially the power at higher rpm) and the speed at which the boost comes on.

Next bit of spare time I get I will carry on turning the pin to see how far it can go before smoke becomes an issue.
Update 5 (18/01/09) - More Fuel
Decided to have another quick play with the fueling so I increased the diaphram and pin/shaft to the 90 degree point, this was a step to far as it constantly smoked when driving, I backed it off to between 45 and 90 degrees and it still produced visible smoke when accelerating so I has to move it back to the 45 degree point (well a fraction more than it was at, lets call it 48 degrees !!)
Update 6 (26/01/09) - 0-60 mph
Finally had the time to attempt a 0-60 sprint in the old corsa, I have an old G tech meter which measures acceleration (using accelerometers), I have tried it out at the drag strip and it was within 1/10 of a second of the actual time so I believe its quiet accurate.
So I went out and found a straight level bit of road, hooked up the meter and gave it a go, considering it was wet I was quiet happy with a best time of 9.2 seconds, this was not totally killing it off the line either so not to bad in my books.

0-60 does not really suit diesel cars as it does not really take full advantage of the torque, the thing I noticed most was the way the power drops off from 4500rpm, I think this is the govenor starting to take effect as it does not just cut the fuel at the required rpm as would happen on a petrol engine it tapers it off as the revs start to get close to the red line. If the point at which the govenor starts to cut in could be raised I think this would have a big impact on the 0-60 time.
Update 7 (01/02/09) - Max RPM Limit
I had previously wound the max RPM screw out a couple of turns but giving it some thought and looking at some exploded diagrams of the bosche ve pump it became apparent that fully winding out the max RPM screw should help to counteract the govenor spring when on full throttle (the extra tension on the governor spring will move the point at which the governor weights will have an effect on the fuelling)

This should help to stop the power dropping off so quickly after 4500rpm, some consideration of course needs to be given to the possibility of over reving the engine (and the screw will need to be re-adjusted at MOT time) but I am happy to take any risk involved.
Update 8 (10/02/09) - Different turbo purchased
Member DutchNovaDiesel on the MIG forums had posted about a different (later) turbo in the IHI RH series that was a straight swop for the turbo fitted to the older 1.7TD Isuzu motor, this turbo the IHI RHF4 VIBD is of ballbearing design rather than journal bushes that the RHB4 has, although the difference in efficiency is probably only small I have been watching out for a RHF4 and finally spotted what looked like one on ebay (turbo and exhaust manifold from a 1997 Vectra), it had a starting price of 99p with 15 delivery, feeling a bit wild I put a 5 bid on it and ended up winning the auction for 2.20 :-)

I have seen the turbo map for the RHF4 and compared to the RHB4 map it is different in a positive way ( I don't fully understand turbo maps to be honest but the RHF4 is closer to the RHB5 map than the RHB4 one, see Isuzu page), from internet research it seems a ballbearing turbo should be around 10% more efficient than a journal bearing turbo, as the turbo should be a straight swop and will only take half a day or so to fit I think it will be a worthwhile modification even for a 10% or less increase.

It is now sitting in my garage awaiting time to fit it.
Update 9 (02/03/09) - Different turbo fitted
It took around 5 hours to fit the turbo plus a couple of hours preperation
The turbo outlet points down but I needed it to point up due to the intercooler pipework, unlike other turbos I have seen this one did not have the clamp type fittings that allows the turbo compressor housing to be rotated to any position, it had fixed tapped holes which when the housing was rotated to the necessary position only 2 of the 5 holes aligned, I had to drill and tap the other 3 holes.

Fitting was as expected, everything aligned ok so it was a straight swop.

I have increased the max fuel slightly with the new turbo fitted without any extra smoke being produced.

Now that I have been driving it for a couple of weeks I have found the following differences compared to the original turbo:
1. On partial throttle the turbo does not spool as quickly.
2. On full throttle is spools quicker.
3. A quick test I did with both turbos - On full throttle from low rpm they both hit 1 bar pressure at around 2200rpm, the RHB4 hit max boost (1.5 bar) at around 3200rpm, the new turbo does the same just before 3000rpm.
4. With the new turbo the boost gauge seems to swing around to full boost quicker and stays at max boost with what appears to be little effort, the old turbo always seemed to struggle to get the last bit of boost.

For the cost/time involved I think it has been a worthwhile modification :-)

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Update 10 (15/03/09) - Water/Methanol Injection fitted
Been reading up on water/methanol injection for a while now and it looked to be a good modification, the average for a diesel engine seemed to be a 15% increase in power with a bigger increase in torque.

I came across a supplier - Devils Own - that seemed to do a kit for a very reasonable price and they had dealers in the UK, so I contacted the UK supplier and ordered a universal kit with dual nozzle upgrade (195 for the kit, 30 for the dual nozzle).

I have fitted it with a 1GPH nozzle before the turbo and a 3GPH nozzle directly before the inlet manifold, the pre turbo nozzle is used to reduce the spool up time, due to lack of space I have utilised the washer bottle as the water/methanol supply tank.

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At the time of writing this I have only had chance to have a quick test of the system, it appears to be working as the washer bottle level is quickly going down, I've set the actuation point at 0.7 bar as I can drive at a reasonable pace without the system activating, going by how quickly the washer bottle went down when testing it would need a much larger bottle if the system was constantly in operation.
Testing was also done using washer fluid (>10% and <30% methanol content) but I have now sourced 20 litres of methanol (99.9% pure) so I can make up a mixture of 30% methanol 70% water which appears to be the optimum mixture for diesel engines.
Two things I did notice when testing is the max boost pressure is slightly higher when the system is active and when accelerating on part throttle when the system activates the boost presure jumps up around 0.2/0.3 bar instantly even though the throttle position remains the same.

When I get chance I will get to a rolling road and get two power runs done (with and without the water/methanol injection) to get an accurate picture on what difference there is.........if any !