Astor XS XU7J4RS (For Sale £1000)

[Dan86]

So this is my new purchase; I couldn't resist a 306 as original and as mint as this.

The plan is to keep it original... apart from squeezing out some more ponies from the aluminium lump under the bonnet.

I am very impressed with the car in standard guise to be fair. It's supposed to have 112hp but to drive the thing you would guess more like 130hp.

The handling is it's ace card; far superior to the Gti6 dare I say it! Having less weight up-front changes the dynamic tremendously. It feels more balanced and feels like there is a larger proportion of weight on the back end. Understeer is non-existent and turn-in is much sharper.

Obviously it's a lot slower than a Gti6 in a straight line but as far as the grin factor is concerned I would say the XS is more fun to drive as you have to drive it harder to get the same effect.

Side by side the Gti6 is the better performance car, but with a nice twisty B-road ahead on a sunny day the XS is a great drivers car.

All this with group 6 insurance and better fuel economy.

Some extra horsepower would definately improve things and would complement the lighter chassis... so I shall be collecting all the parts needed to get the car producing a healthier hp figure.

Some photos of the car at the moment;

[Dan86]

5 hours work;

[Dan86]

New splitter fitted and fogs painted. Also fitted a pair of number plate surrounds; I'm just waiting for some new plates to come in the post.

[Dan86]

I have OCD...












New mudflaps; 306 badges to follow.

[Dan86]

I bought some xsi badges as I prefer the red over the chrome. I cut the 'i' off to make an xs badge with the slanted font.










I have fitted a Gti6 inlet manifold using the xu7 injectors and throttle body. An adapter plate had to be made to make the the throttle body fit. I used some aluminium plate as it's easy to cut/file.










I'm not happy with it.
I took it for a test drive and a couple of times it coughed at about 4500rpm, almost like a carb spits back. It has scared the s**t out of me as I thought it was something catastrophic.

There is also a hesitance at 5500rpm which was always there even before the mani change. I'm not sure what this problem may be; coil pack breaking down? It does it almost every time I try to take it to the red line but on occasion it will go to 6000rpm no problem and feels strong/smooth.

I think I will put it back to standard as I feel it is much safer for the engine.

[vlj]

Looking quite nice, the fog tints are a nice addition!

[C.A.R.]

This is why I no longer recommend the GTi6 manifold conversion. It's worth it on the exhaust side but not the inlet.

You get increased throttle response due to the larger throttle pot, but there is a huge dead-spot like you have already experienced. I'm told this is caused by the ECU becoming confused, it isn't complex enough to deal with the larger intake size or calculate the fuel required properly. Basically trying to operate outside the factory parameters it was set up with.

I turned my last 1.8 back to standard manifolds and much preferred it. Best combination is a nice cone filter for some noise, into a GTi6 exhaust manifold. Lurverly.

PS. really don't bother with GTi6 cams either as this only exaggerates the problems you already have...

[Grant]

Stop trolling everyone who fits a 6 inlet. Scaremongering like this is how forum rumours start. Enty of people have done it with no negative effects.

Oh and cracking car mate, looks great!

[C.A.R.]

Plenty have fitted it and ignored the problems inherited by it, but they are still there. The difference is that some people recognise a healthy engine and a decent powerband whereas others are so blinded by the added under-bonnet bling and the nice noise it gives off to notice that they have actually created a problem, rather than made an improvement.

I'd love to see a dyno-graph from a GTi6'd 1.8 which didn't show a loss in power. They need aftermarket management to work, unlike when fitting the same inlet to a 2.0 XSi, in which case it seems to work to better effect...

[Dan86]

I have used the xu7 throttle body and injectors unlike a lot of the other conversions.

[Grant]

5 hours work;

How did you do that? It looks awsome!

Plenty have fitted it and ignored the problems inherited by it, but they are still there. The difference is that some people recognise a healthy engine and a decent powerband whereas others are so blinded by the added under-bonnet bling and the nice noise it gives off to notice that they have actually created a problem, rather than made an improvement.

I'd love to see a dyno-graph from a GTi6'd 1.8 which didn't show a loss in power. They need aftermarket management to work, unlike when fitting the same inlet to a 2.0 XSi, in which case it seems to work to better effect...

You got any of them dyno printouts handy mate, would be interested to see them.
I will take you out in my car at FCS, and you can make your own mind up. It pulls fine, doesnt hunt, i get no pre-detonation as mentioned above, no knock, just one hell of a bearingy sounding water pump But ill let you make your own mind up, as i clearly have been blinded by the bling and don't know myself.

As mentioned by Dan86 my engine also does feel as if it dips in power at about 5k rpm, but then so did the 2 previous xu7jp4's i had before this, with standard manis. It almost feels as if they are running a form of boost. Its just a characteristic of the engine

A common cause of running issues with this engine is the ECU. There has been a lot about this recently on here, and it is a well documented that goes hand in hand with running issues. If you are insinuating that an XSI should run a '6 manifold no problem, i struggle to see what distinctive differences between the engines have brought you to this conclusion. The engine sensors are the same across the two engines, the only main difference being the engine displacement.
If your going to say about over fuelling, this should not be an issue if the 1.8 FPR and injectors are used. The sensors on the engine controlling the fueling and combustion are designed to work with the FPR and injectors from the 1.8. How would they be outside their parameters? This then leaves us with all that has been increased is the airflow, how is this different to opening the butterfly on the throttle body? Especially in the case that Ben^^^ has used the 1.8 TB.

It just doenst cut it for me until i see cold hard evidence that this mod is bad for a car. Then i will apologize with my coat on. Granted, a remap is needed to gain the full potential of the mod, i do not deny this. But if installed correctly i cannot see how it can cause damage...

[Ruan]

Because at WOT with a gti6 inlet and throttle body, more air can pass through than the standard one... The ECU can't realise this increase in airflow, it doesn't have an airflow sensor - only an idealized table of what SHOULD be going in if the engine is standard...

Added to the fact the ECU knows how much air should get into the engine at a given throttle opening - since it knows the throttle position, so it looks up in it's table of how much air is going in and compensates with fuel accordingly... But it's not the same amount of air it once was because the inlet system has changed... So even at part throttle, it's incorrect.

The ECU is simply a dumb unit full of values that are pre-programmed... A Mass Air Flow sensor corrects this, but still, it has a working range, outside of this range it hasn't a clue what to do.

[Grant]

So from what you say Ruan, it would cause under fueling? Thus a loss in power?

So in Bens case ^^^ how would more air be entering the manifold, with the 1.8 TB? Unless there is an increase in vacuum? As the opening of the manifold still reduces to the same size as previously....

[Ruan]

Well, who knows, the sensors would be telling the ECU things that simply aren't true, so the MAP sensor would be reading values in the manifold to which the ECU thinks is fuelling correctly, but if it's not then depending on whether the MAP is reading high/low it could be over or underfuelling...

With the 1.8 throttle body - it could be doing all sorts of things, possibly more vacuum, possibly less...

Theoretically YES - it should be OK, but I think the combination of the crap ECU and the GTi6 manifold being so much better, the ECU really hasn't a fecking clue what the hell is going on... Not to mention what the heck it's doing with spark timing!!!

[Grant]

Those ECU's have no idea about spark timing at the best of times lol. Not to mention the dispacks. Its a wonder they can detonate anything between them...

The only reason i could see Ben's manifold causing a problem would be from increased vacuum. The manifold is still down to the same diameter at the TB. Air density in the manifold, rotation rate of the engine, and displacement of the engine have remained the same ( i hope lol) so theoretically the vacuum should be the same?

Like i say, I need to see card hold evidence before this mod is sold to me as crap...

[Ruan]

The crap ECU is the cold hard evidence it is fruitless - C.A.R.s old one made 98hp on a set of rollers when I saw it last - it's all down to the pants ECU.

Too many things have changed for an ECU that is picky and unreliable at the best of times. Stick on a Motronic, Mi16 head and get it remapped and come back, I promise, these engines will be fapping awesome with proper management and a decent head.

[Grant]

There was something seriously wrong if his car was running 98. Am I correct in remembering it was an xs?

This is what I am saying though; if the ecu is theoretically fine, running spot on (yeah right ) i fail to see what has changed on bens car to cause the issue c.a.r is saying it is. The inlet is restricted to the same size as previously by the TB, and as far as we know, the vacuum has not changed. Why would the sensors be reading more air?
There has to be an underlying problem, predetonation (i presume this is what ben described earlier by the bangs at 4.5krpm) is never a problem i have heard of by fitting a 6 mani. The only time i had this, was when i forgot the plug the TPS in and the car threw a shit fit...

[Dan86]

I think it is something to do with the pulse tuning of the different manifolds. Both have resonators meaning that some thought went into the design of them. The 1.8 tb is so small I expect the pulse tuning was optimised at a lower rpm than the gti6 one. I guess that the fixed fuelling program in the ecu increases the fuel amount to match the better volumetric efficiency at the lower rpm power band of the xu7. With the gti6 manifold fitted the pulse tuning of the manifold is able to cram more air in at a higher rpm which the ecu can't compensate for making it lean hence the timing being out and spitting back.

If the ecu was able to be re mapped to fuel more to match the tuning of the gti6 mani, I feel it would enable the engine to breath better. The gti6 tb would be better to use if being remapped anyway.

My theories.
Dan.

[Grant]

The longer the distance to the TB the lower the powerband is that the manifold has been designed for. Formula one engines that spend most of their time high up the rev range have next to no runners, whereas you look at v8/v12 engines. You could hide a heard of cows in some of them

I see what you are saying, but following that principle, fitting a resonator bung should have the same adverse affects on a gti6, as fitting a 6 manifold on a 1.8 supposedly has.
IF you follow this principle, you have changed the volume of the manifold air, but the pressure on the back of the valves when shut should remain the same. The vacuum pressure has remained the same (as far as we know) so the pulse waves through the inlet will be ny-on the same.


Also, if you follow the theory that the pulse tuning of the engine is upset by the manifold, fitting a '6 exhaust manifold should see you with the same negative effects as a claimed to be found with the '6 inlet. By that reckoning you would be creating less depression on the back of the exhaust ports when shut, which would leave you with less volumetric efficiency...
This is of-course if the pulse tuning has been upset by fitting the manifold... IMO no, but thats just me

But yes granted, an ecu remap would greatly benefit in this scenario.

I will stop cluttering up your project now, sorry mate. Feel free to ask admin to remove yet another '6 manifold bickering match


P.s Love your car!

[Dan86]

Constructive arguments aren't clutter. It is all valuable opinions so feel free to post some more.

With regards to the pulse tuning; I have always understood that the tuned length of the runner was responsible for the frequency pulses and not the distance from the valves to the tb. The gti6 manifold has shorter runners so would give a higher rpm power band.
Think of jenvey throttle bodies as an example; the butterfly is very close to the cylinder head but by changing the length of the intake runners you can tune it for where you want the torque to fall.

[Dan86]

I would not of said that the resonator changes the volume of available air to the engine as it sits there stale. The resonator may well be there to merely quieten the intake sound.

[Ruan]

The Helmholtz resonator is another form of pulse tuning, it's like blowing across the top of a bottle, air is being drawn in past the resonator space, but then when the air is removed, it sucks more in to fill it's space, but there's obviously inertia when air moves, taking air with it, more than is required causing more air to be entered into the engine - obviously this has to be tuned to a specific RPM/frequency to gain most effect...

Technically, yes, the management could be confused by the removal of the resonator, since it's probably tuned for midrange torque, you'll probably find the engine overfuels very slightly midrange...

The biggest problem with the GTi6 manifold is actually on changing throttle IMO - especially when in closed loop, since the ECU only uses the throttle position for changing transients (i.e. during opening throttle or during closing throttle), that's when it'll get confused, thinking about it more, it's probably quite happy with the MAP readings - it may be slightly out of calibration, but when it goes to adjust for transients, that's when it'll get confused, the airflow in and out of the engine is so drastically changed - whether it's quicker or slower, I don't know, I'm going to guess that the air moves faster, meaning the management responds too slowly to what's actually going on...

There's evidently something that causes this weird running and it's GOT to be to do with the manifold change, I'm struggling for reasons also as to why, but something causes it...

[Grant]

Fair play Ruan. But if the throttle is looking like the most likely culprit, how has Ben found himself with these problems? He has used the jp4 throttle...

Thinking about the pulse tuning side of things too, would the pulse difference of the '6 inlet manifold really affect the running of the engine to the degree previously mentioned? IMO the same suggested problems would be reached by fitting the '6 exhaust manifold, or an aftermarket exhaust with back pressure less or more so than stock... Just giving an incorrect exhaust pulse rather than inlet pulse...

This is of course suggesting that the pulse is the underlying problem here, and I fail to see how a mismatched engine pulse can cause a car to run 98bhp on the rollers....


And yes I have had a few beers. This ^^^ makes sense to me, but i apologize if it is just drivel...

[C.A.R.]

Regardless of what it is that "doesn't work" the evidence shows that on various applications this manifold isn't compatible with the standard management system on the 1.8 engine.

I've seen people use XSI injectors (think these are yellow?) on a 1.8 to try and get it to fuel a bit more, but all this did was overfuel the engine with no 'measurable' performance benefit.

There is no doubt that throttle response is improved and it really livens the 1.8 up, but that's probably due to the enlarged TB rather than anything else (greater density of air at lower throttle position) it would be interesting to compare a 'regular' manifold swap with what Dan86 has done with the XU7 TB.

On the two XU7s I owned with this conversion there was a marked improvement in overall performance when I returned to 'stock' inlet manifold.

I really would like to see a successful installation of both manifolds with a rolling road print-out showing the increased power, however I feel that it really will require aftermarket management before any significant gains are seen.

[Grant]

You've now contradicted yourself c.a.r.

You have previously stuck by the fact that the J4rs inlet causes over fueling. Saying it was this that destroyed your cat... But now you are saying it causes under fueling...

And again here:

There is no doubt that throttle response is improved and it really livens the 1.8 up

there was a marked improvement in overall performance when I returned to 'stock' inlet manifold

Granted, yes a remap would make the most of this modification, to see the proper gains it has as potential. I am not arguing the fact that you may have had a bad experience with this, and I am sorry it did not live up to your expectations. Personally, and this is just my opinion, I feel that there must have been another problem with you car at heart, for it to be running 98bhp on the rollers. Not just the fact it had a '6 inlet.

[Dan86]

I don't think I would be too far wrong to say that each manifold has been optimized for each engine and each ecu mapped to suit meaning that mixing parts without a remap would then mean that the engine is not optimized and would produce less power.
Also 98hp is only a reduction of 12.5% (hope my maths is good) over standard; quite feasable for an engine which is either over fuelling or under fuelling caused by mismatched components.

[C.A.R.]

Grant,

You're beginning to get on my tits now.

Facts:
RS manifold fits onto 1.8
Improves throttle response
Causes flat spots

Unknowns:
Gives a definite performance gain / More power
Overfuels / Underfuels

We don't know whether the flat spots experienced are caused by over or under fuelling, running rich or lean. My car definitely used more fuel which would suggest it over-fuelled, but we don't know whether that accounts for the entire rev-range, without seeing an AFR graph print-out - something nobody has been able to obtain yet.

If you're happy with it then that's good, we're happy for you son. But unfortunately time and time again this manifold swap has incurred 'similar' problems for the majority of end users who carry the modification out.

The above two quotes do not 'contradict' one another. If you re-read more carefully I state that the larger TB imrpoves throttle response, for obvious reasons that anyone - engineering background or not - could understand. However after returning to the standard, plastic intake manifold as found on the 1.8 and 2.0 XSi the 'overall' (crucial word) performance was imrpoved. This is probably because the AFRs were matched better with the parameters which the ECU values are programmed to, so better power and torque could be felt by nothing more than your very own "bum dyno" from the driving seat. Economy improved also, but it was still dire because the aerodynamic characteristics of the cabriolet model are somewhat crap in comparison to a hatch.

Being overly critical isn't the same as having a discussion. I'm keen to know how you have made your conversion work, as you seemingly haven't used any different components to the rest of us. It could be that your ECU is a different model perhaps (I thought the Sagem unit was standard), or that a sensor reading is out. Of course it could be what I suggested earlier in that you might not have noticed where these flat spots lie as yet, depending on how much you use the car.

I'm no engineer and don't pretend to be - I learn by reading and experience. I don't claim to have a superior understanding of the ins-and-outs, but I do have a pretty extensive experience with XU7s in different states of modification and I'll chime in where I can.

[Ruan]

Of course the pulse tuning of an inlet manifold could massively affect the power...

Think about how pulse tuning works - it is tuned for very specific RPMs - this is the difference of pulse tuning:



Notice the dips and peaks in different areas of each line - that's the pulse tuning doing exactly that - if your management is expecting it elsewhere, it's going to cock it right up!

[Dan86]

Great discussion guys! Really loving the passion you guys have for this kind of 'shit'.

After trying the manifold on my beloved car which made it spit and fart gave me two choices;

Return everything back to standard (free)

2. Fork out for standalone management ($)

I felt very nervous about running it not knowing if I was causing undue stress or wear/damage to the engine.

Professional opinions on the cylinder head inlet ports on the xu7 have been that they are"tiny". My opinion when I took the manifold off was that yes they are smaller than the RS head but didn't look very restrictive.

The throttle body on the other hand is about the same size of one of the intake ports!

This makes me think that using the gti6 mani, throttle body and injectors with standalone managment properly mapped would make considerably more hp on a standard head.

Don't some other models use Bosch management like the xsara and 406? It may be an easy way to remapping with the mani conversion.

[Ruan]

The XU7JP4 heads are horribly restrictive, I've heard places they are literally the same casting as other XU heads, but they literally gave them seats and left the head casting alone...

They can be made a SIGNIFICANT amount better by literally taking a drill to the ports, they're so bad as standard, you can get 30hp or so by just playing with the ports!

There's a photo somewhere of Nialls head - you can see the actual ports are almost triangular!

The head is fairly simple to get off - you could have a play, especially if you're playing with management.

And yes, if I were you, I'd look to get a Bosch Motronic system, everything should bolt into place... Even if you steal it off an S16, I know they came with Motronic... Get someone to remap it - you then don't have to pay for "custom" management and have to start from scratch...

Theoretically you could plonk an S16 head on, use the S16 management, and it really wouldn't take much to get a good map from it....