C h a z

What would be the maximum safe boost level to run on my 97 Scooby? I have a revolution 3" bore exhaust and a K&N cone filter. Would I be better off using a bleed valve or shortening the actuator rod. I do have a boost gauge fitted and appear to be running 0.75bar

submannz

Around 13PSI 14.4PSI is the fuel system limit

pat

Chaz,

there is no such thing as a "safe" boost level, sooner or later SOMETHING will let go. It's just a question of what and when. If sticking to the manufacturer's specification then you can expect at least 100,000 miles, probably closer to 200,000 before things require attention internally. If you run more power (notice the lack of the term boost, power and boost are only loosely related) then things will wear sooner. If you get it wrong then the wear will be very quick.

The "safe" boost level really depends on charge density, you might be able to get enough fuel in for 1.5 bar if the density is low, but you may be struggling at 1.1 bar if the density is high. Of the two, I'de prefer to run 1.1 with high charge density, since this will result in cooler running and the possibility of running more ignition advance (and hence more torque). Running 1.5 bar on stock internals is a bit iffy at the best of times!

Please do not use a bleed valve or shorten the actuator. It will give you grief in the end. Only when the entire system is working in harmony will you achieve good reliable power. Decide what you want then get all the right kit to do it properly.

Just as a point of interest, I am getting over 300BHP out of a UK engine at 16PSI boost, and that is still with a stock intercooler (but some other mods ), I hope to get that figure to 300BHP at 14.5PSI boost with decent charge temps (the power run caused intake temps to go up to 70 degrees, which is horrific). With decent charge temps it should be possible to get about 335BHP at 19.5PSI, I don't think I will push it any harder than that... the torque will probably be roughly 310 lb/ft which is a bit ropey on stock internals. If I were to push it to 21.75 PSI that should get about 350BHP and 325 lb/ft torque, but it would probably let go.

At the moment all my breathing mods are slightly at odds with the engine, the extraction is good for 700-1000 BHP, the turbo for 450 maybe 500, but the engine is quite weak in comparison. The result is that the turbo is just twiddling its thumbs even on boost, and it's a little laggy... but then I plan to replace the engine with something a bit tougher, then the system should be better matched again

Sorry if this all a bit vague, but it's like asking "how long is a piece of string?". With a few given parameters, such as TD-04L turbo, free flowing exhaust and filter, stock fuel system, you can run about 17.5 PSI, but don't expect anywhere near the above figures, the charge density will be quite low due to the small turbo. You can probably get to about 250BHP with that, but it's a bit stressed.

Hope this wasn't too confusing,

Pat.

C h a z

Thanks Pat, you seem like someone in the know. What would your next move be? How would you vary the boost/power, not doing the things that I have described?

pat

Chaz,

like I said, the next move really depends on what your ultimate aim is, this way you can avoid making "temporary" upgrades, ie ones which serve a purpose at the time but ultimately won't be much use if the system is to remain in harmony.

As an example, if you do not plan to run more than 1.5 bar (and let's not forget that you can get REALLY good figure at 1.5 if you get good charge density) then a PossumLink would be a good investment. This will give you an immediate increase in torque, a smaller increase in power (limited by the turbo), but being programmable, it will be able to cope with any further work you do, you just need to get it reprogrammed.

If, on the other hand you would like to push it more than 1.5 bar then you would be better off with a MoTeC or similar. The Link will cope with 1.5 bar out the box, but for more you need a 3 bar MAP sensor, and due to the fact that the Link has six pressure rows in the map it becomes quite coarse with the 3 bar MAP sensor, so fuelling will not be as precise. The MoTeC on the other hand has 21 pressure rows in the map, so the degree of control is much finer. You do pay more for this, of course.

I made the "mistake" of underestimating what I eventually wanted to do, and I bought a PossumLink. I was very pleased with it and got some really good results. But the old tuning bug bit harder than I anticipated and now I want to run upwards of 2 bar which I cannot with the Possum, so I have sold it and bought a Pectel T6... out of the box the pressure sites extend to 4 bar boost

Just as a rough guide to costs, last I looked the Possum on its own was about UKP 650, the MoTeC on its own UKP 1580 and the T6 about UKP 1850. I discounted the T10 as the entry level (there are many options) was about seven grand! All of these will require extras. As a minimum I would suggest a LambdaLink and a KnockLink, they will cost about UKP 200 for the pair, but they can save your engine by warning you of something not being quite right before it does any damage... much cheaper than a rebuild or a new engine!

The MoTeC and Pectel will require loom adapters, they are not a drop in replacement (see Autronic for MoTeC-like features but drop in unit) they are general purpose, very highly configureable but of course this means you need to connect the right wires on the ECU to the right ones on the car!

Both have untouchable credentials.... the MoTeCs have powered GT and rally cars to victory, the Pectel is used in touring cars and on the Ford Focus World Rally Car, which doesn't do too badly

You already have good breathing on your car, the turbo will limit power, but an ECU an remap will certainly unleash more torque (this will happen in the midrange, where the turbo isn't really stressed anyway). If you really are only running 0.75 bar then there may be a fault with the wastegate control, or you may be running premium unleaded and your ECU is pulling back the boost as the engine is pinging. If you go to 1.2 bar then that can liberate up to about 60 lb/ft more torque, which will feel *VERY* strong in comparison! With this setup, you have nice upgrade path as well, by replacing the turbo you can unleash even more torque and power, yet REDUCE the boost needed to get it! One car I know made about 290BHP at 16PSI, mine made over 300 at 16PSI (about 1.1 bar).

Hope this helps,

Pat.

C h a z

Thanks Pat, are there any web pages that you could recommend to read up further on this subject? There are many options it would appear. Thanks again for all your help so far.