Over Boosting!

[Guest dico2020]

whilst fatz and mucus-t were playing with thier flaps on saturday, I popped around to headsex's to clean up my tune and do some data logging after fitting an x-force 4"dump, 3.5" single.

we were excited to see the boost at an uncontrollable 20psi, even though my gates been ported to within an inch of its life!

so im looking forward to getting an etm external wastegate and screamer pipe, and one of his remote turbo oil filters.

anyone else had this problem and had to chane to an external?

oh and envy-t, when you hear people talking about a fat poof, dosnt always mean their talking about you!! hahaha

[Fat-Tony]

Shut your chin ramjet.

[ENVY-T]

Hey you, be a man!!! Centre your cannon tip! And don't worry mate, the marrige charade is wearing thin, your mum is starting to suspect the truth!

[SCRIBR]

How would a screamer sound on the Yaris?

[senna_T]

it would probably be pretty quiet most of the time, it wouldn't spin a 3540 up until 9000rpm!

[Nizpro]

Below are a couple of posts I responded to regarding the costs of modifying the turbine waste gate for the XR6T, please don’t take them out of context or a shot at any other performance workshops as this is not how they were intended and I think I got myself off to a bad start with Jim from XR6 Turbo Developments as he thought I was having a shot at him. I wasn’t, however I was explaining the reasons of why I believe you need to do more to the housing than is typically thought for the very reason of over boosting.

I have now looked and have seen a number of guys here that have had waste gates modified and are still experiencing over boost conditions. Most people and even some tuners believe that the waste gate is modified so you can stop boost drop off in the top end, this is not the only reason as some are now finding out. The normal die grind it out method simply does not work once a low restriction intercooler and exhaust is fitted. The tune can also play a role in over boosting when the waste gate is not ported or machined correctly.

The waste gates job is to by pass air from the turbine wheel straight to the exhaust system, the engine’s air flow characteristics can also change even at the same boost levels and rpm depending on the tune and in particular the ignition advance a “safe” tune with too little advance will tend to over boost more than an engine that is correctly tuned. This is why dyno tuning is very important vs road tuning. A couple of extra ignition degrees retard can certainly make the over boost problem uncontrollable, of course this is a catch 22. With over boost you need more spark retard and in turn this causes more over boost. This can some times never be fixed with tuning and the waste gate needs to simply control better.

The better the components the more important it becomes and as I posted some weeks ago Nizpro believe that doing the job to the highest level the first time is always the better decision, as doing it twice simple costs more than doing it right the first time and this is what I was trying to explain, as customers need to be fully aware of the modifications vs price paid.

So without trying to offend any other site sponsors as once again this is not my intention lets look at external waste gates. Will this fix the problem and what effects will it have.

Back it 1992 I fitted external waste gates to cast iron or steel manifolds on the R31 skyline or Vl Late model camira rb30 engines for pretty well all the reasons we still have 16 years latter. Now the Nissan casting are made from really good material but over time I still had problems with them cracking due to the different expansion and thermal rates of the different materials. Now the RB30 manifold leads itself to having a external gate mounting on the top just before the turbo this made it reasonably easy to mount and the waste gate was not physically being supported and yet we still had problems. On the BA/F engines they will have to be mounted in the position where ETM are putting them on the turbine housing for packaging.

Now over time and I am happy to be wrong however experience tells me that they will be prone to cracking, especially seeing that the turbine housing is not very thick in the area and it is where the temperature will be the highest.

Secondly as a performance stand point in regards to power, theoretically this is a very poor place for a waste gate to be positioned. Boost control wise it will work well but as far as getting the best performance goes it will be very poor compared to having it mounted before the turbocharger itself.

This is due to having high back pressure at the waste gate and turbine housing, on the one hand this is why the boost control will work well but as for an engine stand point you have now increased back pressure in the turbine housing that will not be used for turning the turbine wheel and then let it waste. It is far better to have the waste gate further up the system and get rid of the exhaust gas before the gas enters the turbine housing as it is this point where the back pressure rises. The more back pressure the less power.

So if you can get rid of the excess gas in the manifold via the waste gate and only send what is necessary into the turbine housing the more power you will make. You will need a big waste gate as the pressure will be low so you need a bigger hole to get rid of it, this needs more room and it all gets hard.

So the best answer to boost control while using the standard manifold and turbocharger on a BA/F is to stick to what we have and although the standard waste gate is also mounted, although internally in the turbine housing it is at the highest point before the turbine is starting to get smaller. This is not ideal but it is as good as it gets without a complete manifold and turbo package. It is also some thing that can be made to work very well without all the above complication.

Cheers Simon

From older posts

There is considerably more to modifying the turbine housing than just die grinding the hole out and fitting a larger flapper depending on what you are trying to achieve.

Firstly with the age of the turbine housing ranging from 6 years old to new many are now cracked around the bolt holes that hold the Core [CHRA] to the housing, this is why many people find these bolts coming loose or even falling out. There are reasonably reliable fixes for this but each housing needs to be inspected and assessed before carrying out work on the housing.

Many people and companies can simply grind by one method or another the hole out and fit a larger flapper and we have seen that the results in some cases still lead to over boost conditions if the vehicle is fitted with very good exhaust and intake plumbing. I believe both Ali from BTA and Paul from Elite have experienced this with there higher powered cars when using housings from other suppliers. We also saw this type of issue early in development when doing a similar job.

Our main push with getting these housings to work very well was when we were asked by a GTP F6 customer that needed accurate boost control for the GTP Championship. As the boost limit is set at a very fine tolerance due to the rules and any over boost causes disqualification. The officials also wanted every housing machined exactly the same as they did not want a competitor to have any advantage over overs. At this point we decided to cnc machine all the housings. Being that the exhaust systems are free and that the boost limit is set at 9.3 psi accurate boost control is paramount. Without careful design of both the shape of the exhaust port hole, ours are no longer round as a round hole did not flow as much air by bass as our current shape and the selection of the waste gate actuator. The throw of the actuator is also important as most common waste gate actuators only throw 15 mm and we found that this was not enough to get the flapper far enough away from the hole for good flow.

Lastly there is another tick we do to get increased turbine flow that adds around 15 rwkws at about the 380 rwkw mark when things start getting hard.

Bottom line: Turbine housing mods including cnc machined housing with 38 mm stainless steel flapper up from 32mm, correct waste gate actuator with long travel and machine turbine housing supplied and fitted as a change over is $1180.00 this also includes new muti shim s/s turbo to manifold gasket 4 new inconnel studs and nut to prevent them from coming lose as many of you experience. Supply only change over is $780.00

No doubt these prices are more expensive than overs charge but I hope the above explanation clearly explains that there is a little more to it than break out the die grinder if you want the best possible result in boost control and increased power.

Cheers Simon

Sorry Jim if you took this as a shot at you as it was not meant to be. The tread asked about the cost of turbine housing modification and I believe a full explanation is needed for people to fully understand the large difference in prices from a simple port job to a fully developed modification.

“Regardless of wheather you die grind the housing or use a CNC process to enlarge the hole ultimately you will achieve the same result which is opening up the waste gate port to enable gases to be vented more efficiently”

Unfortunely, this is simply not the case as further experience will show you. Just like large gains can be made in porting a cylinder head in terms of air flow the same can be achieved with careful design and shaping of the waste gate opening.

The pricing not only refects the cost of the parts but also development time in making sure a modification works under all circumstance. As I explained, we also used similar methods earlier on but found that it still caused over boost problem on large output cars. You make mention of a actuator not holding onto boost, this is not what I have explained in fact it’s the opposite. On high kw cars the boost will actually get away from the desired boost level and sky rocket into the low 20 psi mark. This is where the extra time and effort along with a more expensive actuator is needed. I ‘m sure you will come across this in time, just as the others I have mentioned have.

Customer need to have all the information presented to them so they can understand fully why some modification are far more expensive, although on paper or in advertising they seem the same.

It is correct that some don’t need to go to the extreme levels, however Nizpro is a big believer of doing the best possible job the first time round as it is more cost effective than having to re-do it a second time if the customer choses to go further than they anticipated with their levels of modification.

I hope this clears my response up.

Cheers Simon

[senna_T]

All good knowledge you are sharing with us there Simon! I know you mentioned the old Power vs. Price issue, and I think ETM has adressed this pretty well with a realtively budget conscious solution to boost control. I also beleive that ETM has a Full custom high mount manifold with external gate provision - this shoudl be a good package once released and tuned on a vehicle with the engine to support it

[Nizpro]

All good knowledge you are sharing with us there Simon! I know you mentioned the old Power vs. Price issue, and I think ETM has adressed this pretty well with a realtively budget conscious solution to boost control. I also beleive that ETM has a Full custom high mount manifold with external gate provision - this shoudl be a good package once released and tuned on a vehicle with the engine to support it

Absolutely as a said this is not a go at ETM, I don’t even know how much they charge. I simply mentioned their name as they are one of the companies that are doing this kind of mod that I new people here would be familiar with. However it dose not matter if its ten bucks if it falls off and you drive over it. Now this may not be the case as I said I am happy to be wrong and ETM I hope have already done this modification and tested it on their cars for a reasonable amount of time to make sure that they work well, I'm sure a company of their standing will have.

I am simply explaining my observations with these mods over the last 20 years and the positive and negative results I have seen with them. The question was about over boosting and who still has it after modifying the waste gate. It appears quite a few.

There are ways around it and one of them could be with an external gate, but when a correct mod is done to the standard internal gate it function extremely well and cannot suffer from the failures I have spoken about above.

In my experience the people that are suffering from over boosting have simply not got the correct mods done to their waste gates and it will now cost them money the second time to get it fixed correctly. Either with an external sep up or with a correct internal one.

Below is an example of how cheap pricing can cost more with an poor decision made alone on price

Headsex said this a few months ago

I do believe some turbo companies do a "exchange" program.. But enquiring to two of them, they were talking around the $350 - $400 mark.. bit rich in my opinion..

Danny

Now this gives consumers the opinion that 400 bucks is too expensive and that they can be done for less and yet Nizpro complete waste gate and turbine solution is $1180 drive away. The difference is ours works perfectly due to the parts we used and the development and testing we have done. If Headsex’s solution was $200 and it didn’t work its no longer cheap as some are now finding out. The next problem is that once these housing are incorrectly machined and if you still have over boost issue’s we cannot fix them so the housing is a throw away. A new housing is about $700 plus what you spent in the first place plus the remove and refit and you still have you get it fixed.

Now I don’t know who Danny uses or if he does them himself or who he was referring too I just used his quote to show how one person opinion who has little experience can influence peoples decisions only to find out latter it has cost them extra money to get the desired result. Consumers need to make sure they get proven parts for a proven result for a fixed amount. There will always be more than one way or the Nizpro way to fix a problem but please don’t base your decision on cost alone as its can be an expensive way to learn

Simon

Edited 05/05/08 04:57 AM by Nizpro

[SCRIBR]

I always was a bit dubious of the dremel approach to wastegate mods... how can it seal perfectly?

I assume Nizpro bores out their wastegate enlargements?

[ETM]

I have done more wastegates welded on garrett housings than I can remember and never had 1 crack.

I have never had 1 crack in anything ive ever made to be honest