Bottom End Power Xr6t

[scott52]

MAL BA XR6T, yes ive got the XR6T and yes I have a boost gauge installed (have a look at my post under modifications for a photo of the mounting).

The valve I used was not really suitable as a boost controller - but I wanted to see the effect of restricting the wastegate hose after reading the articles on autospeed.com.au. I agree with turbo6man that a turbosmart or similar valve is the way to go ie. something designed for the purpose.

[F6 RAPID]

Thanks RichDave.

If only I put as much time and effort into work as I do cars and bikes...............

[Guest esky]

Look into an electronic boost controller or a simple boost bled valve from Turbosmart will do the same thing for around $110. These things do help low down and part throttle response remarkably. I have done these mods to a previous turbo car and have had excellent SAFE results.

Can you explain how you get a greater low end response from a few psi more from this approach? As this doesn't deal with lag. And that's what causes the poor bottom end power.

Have you dynoed your car, to see the results?

You will be able to get a boost graph on your dyno figure if you ask your dyno operator.

[F6 RAPID]

Esky,

Without spending an hour typing trying to explain tuning of them, this is the crux of it.

The wastegate on your car is actuated by a pressure diaphragm (that is the shiny gold cylinder thing with a small pressure hose attached). When the turbo starts building boost (which could be as slow as 1000 - 1200 rpm) the diaphragm partially opens and starts to bleed off the boost and it will be fully open by 6psi. This allows a smooth transition through the rev range with no "peakiness". It is good for smoothness, not good when you want instant boost - like you do.

By plumbing in a bleed valve (and doing the tuning), the valve itself intercepts the pressure from the compressor outlet before the diaphragm. The bleed valve will not let ANY pressure through to the diaphragm until it reaches its pre-set level (psi). So, even if you retain the factory 6psi, it has the effect of boost building MUCH sooner than the stock setup because there is no boost bleed before reaching it's peak setting. Not only does this vastly improve your bottom end, the part throttle response (as previously mentioned) is excellent.

This is how the bottom end is fixed (improved at any rate - fixed is a personal representation) - very simply. This is from a previous post of mine earlier. Also, go to Autospeed (following my previous directions) and read about Wastgate creep. If you can eliminate that, it dramatically improves your bottom end.

[Mals BA XR6T]

MAL BA XR6T, yes ive got the XR6T and yes I have a boost gauge installed (have a look at my post under modifications for a photo of the mounting).

The valve I used was not really suitable as a boost controller - but I wanted to see the effect of restricting the wastegate hose after reading the articles on autospeed.com.au. I agree with turbo6man that a turbosmart or similar valve is the way to go ie. something designed for the purpose.

Scott, Just out of curiosity for myself, and of course others, just a couple of additional questions

1. Did the boost actually increase at lower revs... and if you know, what was the increase...eg before 2000 - 2psi, after 2000 3psi

2. How high did you run the boost, and why did you think it was going to break... was it pinging, or making strange noises??

Thanks mate

[CJF077]

Im interested to know as well.

[Turbo6man]

Coming from a V8 I miss the bottom end power... can anyone suggest changes to help get the XR6T's bottom end power up a bit.. type of exhaust etc???

The difference you are noticing is torque. You will never achieve the same torque at idle from a smaller displacement engine than one with larger displacement and which also has two extra cylinders. This is simple physics. However you can improve the efficiency of any engine at lower revs by changing cam profile, cam timing and ignition timing. Of course the trade off is less performance at higher revs.

Now, with the 4.0 l engine which already has ECU fuel and ignition control and also variable cam timing, little (if any) gains will be achieved.

The only practical way with this engine would be a split turbo system which someone has already mentioned. The way to do this is complicated and not cost effective but if you have the money it can be done. A small turbo running off the front two cylinders will give boost right at idle, the second running off the remaining four cylinders gives the higher rpm boost from about 3000 rpm. Most manufacturers who have played with these systems have given up on them due to cost and complexity - the end results from a well set up single turbo is generally acceptable for all but max performance competition use.

Your best alternative is to play with gearbox and diff ratios - leave the engine alone as it is actually set up quite efficiently as it is. A diff ratio change to 3.9 will give you the same off-line response as your old V8.

PS. scott52> pls stop referring to turbo6 as me (Turbo6man) I do not want to be attributed with condoning the mods that others have expounded in the thread.

[Ninka]

Coming from a V8 I miss the bottom end power... can anyone suggest changes to help get the XR6T's bottom end power up a bit.. type of exhaust etc???

The difference you are noticing is torque. You will never achieve the same torque at idle from a smaller displacement engine than one with larger displacement and which also has two extra cylinders. This is simple physics. However you can improve the efficiency of any engine at lower revs by changing cam profile, cam timing and ignition timing. Of course the trade off is less performance at higher revs.

Now, with the 4.0 l engine which already has ECU fuel and ignition control and also variable cam timing, little (if any) gains will be achieved.

The only practical way with this engine would be a split turbo system which someone has already mentioned. The way to do this is complicated and not cost effective but if you have the money it can be done. A small turbo running off the front two cylinders will give boost right at idle, the second running off the remaining four cylinders gives the higher rpm boost from about 3000 rpm. Most manufacturers who have played with these systems have given up on them due to cost and complexity - the end results from a well set up single turbo is generally acceptable for all but max performance competition use.

Your best alternative is to play with gearbox and diff ratios - leave the engine alone as it is actually set up quite efficiently as it is. A diff ratio change to 3.9 will give you the same off-line response as your old V8.

PS. scott52> pls stop referring to turbo6 as me (Turbo6man) I do not want to be attributed with condoning the mods that others have expounded in the thread.

Exactly right, a turbocharged car is a completely different "beast" compared to a V8, and as you point out, can never have the same torque at idle.

I used to drive a 5.0 V8 before the XR6T, and I notice the difference off the line, but once the turbo is on boost, man is it quicker!!

All I can say to people trying to extract more power from their XR6T, BE CAREFUL, a turbo has the potential to seriously damage your engine/transmission, and you would be wise to wait for a reputable company to come out with kits that are tryed and tested to ensure you do not end up with non warrantable grief!

[Guest]

I think the problem is your missing two cylinders. If you want low down grunt that's what V8's are for.

[bcl]

Thanks Turbo6man, one of the more sensible responses for a while in this thread.

To your response I would add the alternative of a stroker kit to add cubic displacement, which is an expensive option, and possibly not available for a while on the Ford.

The main aim for major drivability (as opposed to maximizing power) is faster turbo spool-up. At the moment there are too many unknowns with regard to what Ford has built. With REXs, GTRs, 200sx etc there are many years of experience to know what works and what doesn’t.

To your response I’d add that gas temperature (which impacts exhaust gas flow) is an important factor in turbo spool up. Generally this can also be changed by modifying timing and fuel mixtures. An EGT gauge helps here.

The exhaust manifold design looks a bit crude and no doubt will be redesigned by aftermarket people, and a split pulse turbo (which I’m not aware is currently used).

The dump pipe design also helps, and we’ll find out soon if the dump pipe design uses the split gas flow technique commonly used by aftermarket systems. (I doubt it does) The size/restriction of the exhaust system will also help spool-up. I’ve had many 3” low restriction systems, but my favourite is 4” with dual straight-thru mufflers for less drone and better low-end response.

No doubt others will play with different compressor designs.

I’m sure there are many things that will improve turbo spool up, and give a good increase in torque between say 1800 and 3000 revs. It’s quite amazing how often with factory version can be substantially improved.

Someone also mentioned wastegate creep. I doubt that it will be a factor with only 6 pound…. This is more a problem with 1 bar or more.

People that have not had turbos before, but only V8’s, will find that this a totally new ballgame, and a lot more fun. Also there are quite a few relatively inexpensive things that can be done for improved performance.

Don’t worry too much about lack of grunt, just drop a gear; the V8’s will wonder what hit ‘em.

Brian