Supercharging the 400 SX

[Engineer1949]

thought i would run a little thread on the supercharging of a 400 sx using a rotrex system for pre serp engines i developed for the orange chimaera i rebuilt three years ago, first problem was getting the old sprintex drive off the crankshaft pulley all the bolts severely siezed ended up cutting two off, then removed the old existing plenum and base as they are just not up to sopercharger pressure being very poorly laid up carbonplus the base is much wider than the original, then mounted the blower to get the alignment sorted as it has a massive trigger wheel mounted on the crank pulley but it just goes, the belt run will be close to the trigger but not impeding its operation, then centred the pulley on the lathe took a reference cut on the register so as my pulley will be perfectly square and centrally mounted, then started the machining to mount the pulley for the rotrex which i just finished last night.

john

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[adam quantrill]

Make sure you keep all the old parts - someone could make another 400SX!

So - no teeth on the pulley? Not a toothed belt then?

[mrzigazaga]

Smooth pulley...Doesn't a smooth pulley need a "Crown" or flanges to aid belt alignment?....What about the other pulleys..Water pump, Alternator, PAS?

[Engineer1949]

this is just a start it will have a seven line multi vee just like the serp engines but havent got that far yet maybe tomorrow


john

[mrzigazaga]

Looking awesome....

[boxer456]

Engineering as it should be done, wish I could make stuff like that!

[Engineer1949]

good day today finished turning and fitting the crankshaft pulley wheel both for the blower and the auxiliary belt well pleased with the result, pics tell a better story.


john

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[adam quantrill]

If you are making new mountings for the blower here are two bits of advice:

1. Don't attach the mounting to the cylinder head bolt - it leads to head gasket failure at the number 1 cylinder to water jacket gap.

2. Don't attach to any water pump bolts - or if you do, add strengthening bars to brace back to the other bolts. Or else the vibration/torque can crack the pump casing.

I added a mounting bracket attached back to the block - there is a lump coming out of the casting with a handy hole in it and I used 1" square steel tube to transmit the mounting forces back to the block and avoid the cylinder head.

[Engineer1949]

Thanks for that adam not sure which blower these tips are for i am fitting the rotrex which has a bespoke mount which uses the large tapped holes in the front of the head some models use them for the aircon pump,fitted several and never had a problem the old sprintex did use a bracket on the head bolt which is not a great idea.


John

[adam quantrill]

It's what I learned from the Sprintex mountings which work OK, but eventually cause problems, so I have subtly fettled my installation to work around them, while keeping it looking original.

However I am talking proper long-term mileage here, 10, 20, 40k miles, if you're only going to be doing a few thousand a year then these considerations are less important - less likely to cause a problem.

I would say that a blower vibrates much more than an aircon pump - also the torque transmitted to the engine is much higher because the belt loading is ten time that of an aircon fanbelt drive.

But if you're not doing high mileage - bolt onto the head.

[Engineer1949]

the point here adam is the rotrex is a rotary supercharger basically a turbo stile compressor driven by a gearing up gearbox they are superbly smooth and quiet and use nothing like the power of a traditional positive displacement unit the 4.0ltr chim i did three years ago has had good mileage put on plus lots of track days and quarter mile runs and no ill effects.


john

[mrzigazaga]

The rotrex are centrifugal blowers whereas the Sprintex is a twin screw...I take it the rotrex units run cooler intake temps?...What psi will you be running it at...All looks very well engineered...

[adam quantrill]

It would be interesting to see before and after torque curves on the dyno, too.... (less interested in power, torque is where it's at). For the Chimp that is.

[Engineer1949]

just a small job sorted today got rid of the unused dizzy cleans the engine up a lot.


john

DSCN1967 by Brundall Motorsport, on Flickr

[Engineer1949]

hi zig we should get about 7psi with the current wheel on the blower there is a slight concern that the pipes to and from the intercooler are smaller than i would like but at these pressures should be ok, as a rule of thumb every bar in pressure theoretically increases power by 100% never is quite that with mechanical losses etc. so 7psi should give a good 50% increase so looking 300plus if the injectors and ecu are up to it, and yes inlet temps are lower as the air isnt being constantly squeezed when not needed.

john

[Engineer1949]

sorry adam cant do before after as the original blower is scrap but will post curves once finished

john

[mk1fan]

Given your skills - mechanically, your driving is appauling, can't even finish a sighting lap without spinning - have you thought about replacing the water pump with an electronic version?

[adam quantrill]

adam quantrill said:

For the Chimp that is.

[griffdude]

adam quantrill said:

adam quantrill said:

For the Chimp that is.

Scroll down a bit on this thread-

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[adam quantrill]

Cheers is that the NickOrangeTVR one? In which case that's quite a peaky torque curve compared with the Sprintex.

Incidentally we do have the Sprintex dyno figures for the "Black Elephant" as Martin's car was nicknamed. It was on the rolling road at BBWF and turned out around 270 bhp as I recall. Martin may have posted up the graphs...