Head Difference Tu3s And Tu3m

[snillet 1]

Since people might not have spotted my followup questrion in the end of the rallye-head thread, i post a new one on THIS subject.

 

What is the main difference between the heads on the TU3M (Bosch monojetronic 75hp engine) and the TU3S engine ?

Please enlighten me if for example it´ll be worth the effort to use the XS cam in that engine for better top power ?, or is the whole head better ?

 

The injectionunits 38mm throttleplate is a restriction in itself but it´s easy to bore out to at least 45mm, and a have a bunch of different throttleplates laying around, and i know how to beat the revlimiter at 6800 as well if that´s needed. The manifold isn´t that ba for reaching up to about 80-90hp i think, even the throttlediam might be enough if you do the usual 10mm2 throttleplate area per 1hp estimation, but a little less restriction wouldn´t hurt anywhere really.

 

So... the heads, differences ?

[AdamP 0]

I *think* the inlet port spacings are different.

[Rippthrough 98]

The inlet spacings are the same, but the XS cam is slightly better, I've got them both around here somewhere so I'll have another look later, but I ended up going with the XS head for some reason, can't remember why though

 

 

How are you getting around the rev. limit on the Monotronic? It's at 6200rpm, no fun!

Edited February 19, 2009 by Rippthrough

[snillet 1]

The inlet spacings are the same, but the XS cam is slightly better, I've got them both around here somewhere so I'll have another look later, but I ended up going with the XS head for some reason, can't remember why though

 

 

How are you getting around the rev. limit on the Monotronic? It's at 6200rpm, no fun!

 

 

Ah, yes 6200 it is yes.

 

You can fool it by replacing the 6mHz clock-crystal to a higher value, that also brings up the idlerpm and shortens the injectiontimes though. It shall be a linear function to the frequency regarding a dutch guy that found this info from some AX tuners in Austria...., this has been discussed on a Swedish Ethanol(E85) fuel and conversion forum where the issue was to increase fuelamount by lowering the frequency, but it works in both ways. Those AX people bored out their Monojetronic Throttlebodies to about 55mm ...

 

So it´s quite easy to overclock the processor to reach over 7000 and even up to 8000 as revlimit if you do some simple math on it and assuming the function IS linear. The idlerpm is in my opinion not a big deal if it increases linear either, if you move the revlimiter to 7200, that means that the idlerpm should increase to about 1050-1100, i can live with that, And the fuelamount is easliy regained by a slight increase in fuelpressure by putting shims at the regulator, might even put it on a bit extra to cover for the hp gain you´re expecting at the top

 

So you´re saying that the heads aren´t really very different but the "S" head has a more aggressive camshaft ?

 

It is somewhat confusing with the TU3M, cause there are different versions of it, KDY/KDZ/KFX is the most common ones, and they´re all called TU3M...

For example in Sweden the cat engined Citroën BX has a TU3M engine that´s specified as 80bhp, and the standard 205/106/AX has a TU3M specified as 75BHP.

 

The TU24 camshaft (eurospec rallye) is a bit to wild for this project, so i´m on the outlook for the wildest "standard" camshaft. And if the HEAD is also better on the TU3S engine, i might as well use that one.

[snillet 1]

Ok, after review this website: http://www.suzukituning.com/PSA/TU3Tuning/TU3Tuning.htm

 

And this document, which is a specification for the TU3M KDZ engine in the Swedish Citroen BX, and the engine that my questrion is "about" is actually that engine, although right now it´s in an AX and will be moved over to my 106 *lol*, lots of moving around for that engine...

 

The revlimit actually is 6800, and the camshaft seem to be THE SAME as the K2A engine, and in the registration papers all these BX:es in sweden has 59kW, and that is 80Bhp ,things don´t add up here.

 

I have a gut feeling that the KDZ and the K2A is VERY similar except for intake system and compression.

[Guest demios]

I have 205GT and have put TU3M in it, because the old TU3S died (head gasket went), so I took the engine from an Citroen ZX.

I do not know, honestly how to determine which cam this new one has, because all ZX's have 75hp engines with monopoint injection and all variations (KDX,KDZ,KDY) are made in the sam period of time. Now, I'd like to know is it possible to find out which cam i have, without opening the engine? And, another small Q:

 

What needs to be done on an old TU3S to increase it's compression to 12:1? I know i have to change the head gasket, even out the head, probably change the rings......I think honing is necessary, and some minor valve job. Now, do I need to increase the head flow, change the pistons....what is needed to make it a dragon ?

 

Thanks in advance, guys!

[snillet 1]

Ok, after review this website: http://www.suzukituning.com/PSA/TU3Tuning/TU3Tuning.htm

 

And this document, which is a specification for the TU3M KDZ engine in the Swedish Citroen BX, and the engine that my questrion is "about" is actually that engine, although right now it´s in an AX and will be moved over to my 106 *lol*, lots of moving around for that engine...

 

The revlimit actually is 6800, and the camshaft seem to be THE SAME as the K2A engine, and in the registration papers all these BX:es in sweden has 59kW, and that is 80Bhp ,things don´t add up here.

 

I have a gut feeling that the KDZ and the K2A is VERY similar except for intake system and compression.

 

Have seen a reference here at this forum that the TU3S head has a "3S" in the casting.

Found this on front of the KDZ engine i´m mentioning above:

(yes i know it´s oily and gucky, i just got it home...)

 

Does this mean my above conclusion is VERY close to the truth ?

[Guest demios]

I'll take a look at my TU3M and report back.

[holland_gt 0]

Hey guys, ive got a the gtx 205 with singlepoint injection aswell and i was wondering what could be done to push the 75bhp up a bit. I bought a solex dual choke carb from the AX GT to fit but in all honesty I can't be botherthed any more but bore-ing the throttle plates and that sounds a good idea. Is there any guides to do this or is it trial and error? thanks, James

[snillet 1]

Hey guys, ive got a the gtx 205 with singlepoint injection aswell and i was wondering what could be done to push the 75bhp up a bit. I bought a solex dual choke carb from the AX GT to fit but in all honesty I can't be botherthed any more but bore-ing the throttle plates and that sounds a good idea. Is there any guides to do this or is it trial and error? thanks, James

 

I´m digging deeper and deeper into this.

The best tip i can tell right now seem to be to adjust so that the ports in the manifold matches the ones in the head, the production of the "M" manifolds are pretty bad, so the portmatchin can be better, and while you´re at that you might aswell reshape tha whole thing to a better function.

 

And then the throttle plates, look into what other brands with Monojetronic uses, for example within the TU range the TU9M has 30mm plate/ 24mm runners in the manifold and 24mm ports in the head. The TU1M has 36mm plate 26mm runners and 30mm ports in the head , strange...., and the TU3M has either the same as TU1M or 40mm plate /30mm runners and 33mm ports in the head.

 

The diameter differences on runners and head is not matched, so just smoothing out THAT transition should give a wast improvement in enginefunction.

 

The VAG unit used on some 1.8liter engines has a 38mm plate and is easily bored out to about 44-45mm, which is what i plan to do, i´ll nick the throttleplate from a XU9M throttle housing that i have in the "could be good to have sometime" bin, i also have the VAG unit there .

 

I´ll leave the head and intake manifold to a friends friend of mine that seem to have quite good hands with machining of heads, the last one is a boosted TU3J2 with 220wbhp on just 1.5bar boost. The TU is VERY responsive to basic tuning, it´s a very well engineered unit from stock.

 

Opposite to the gearbox they fitted to them, the MA *lol*, not so solid engineering that one.

[holland_gt 0]

Opposite to the gearbox they fitted to them, the MA *lol*, not so solid engineering that one.

 

Atleast they got something right! It's french after all, anyhow seen as I have a full gasket kit laying about I might match the port sizes as you suggested, I've heard that working on the exhaust manifold and removing the nasty lumps out of it can help aswell. Might spend a nice day or two on the engine and just try and restore some ponnies under the bonnet!

[batespeed 0]

very interesting, any progress with this guys ?