DeanM

Here is my take on the DTA P8. I have had my DTA for a couple years now. I have only had experience with one EFI (DTA) so far. So I am not a tuner at all. So take this with a grain of salt.

I have found the DTA to be an ok system. I have had trouble getting a cold idle. I also think the lambda system sucks. Now it could be me, but my fuel correction map is ALWAYS trying to lean out the motor. I can work around the problem with certain settings but I don't think I should have to. I paid for a system with a fuel correction abilty and haven't gotten that to work yet.

I also find the support from DTA in England sort of stinky. The engineer over there seems put out by my questions.

I also have problems with the ECU talking to Windows. The DTA engineer says it is Windows fault.

If I were to do another EFI system, I would choose a different brand so I could have more experience with different brands. So I don't know how the DTA compares to other systems yet.

Good luck
Dean

ZX3tuning

good info.
basically what i was thinking was to run ITBs into a shared Plenum fed directly off the IC outlet.
Granted i have played around with ITBs on other cars but never a Porsche so i really have no idea what i'm getting myself into.

as far as the trouble....
how so?

mapping ITBs on a NA setup can be very difficult because of the TPS and MAP tables but if i'm running a shared plenum setup then wouldn't that be the same thing as running a single TB 964 plenum just with a TB per cyl? I could build the ITBs, IM and Plenum to accept the factory or even the DTA sensors which would make basically the same as tuning with a 964 or similar IM, no?
I was thinking of using the Curved SS trumpets, cutting a 4" SS tube in half and then boxing it out to a 2700cc oval-shaped plenum, slipping the trumpets through the inside of the plenum and leaving about 1" of the trumpet extending INTO the inside of the plenum before welding the trumpts to the plenum itself.
i could easily build and weld bungs onto the Plenum, trumpets or anywhere they are needed.
obviously i'd need to fabricate a new inlet pipe and weld bungs and nipples onto it for the required Vac triggers and such.

i dunno, just thinking of what i can do.
the time and effort isn't much of an issue, i have lots of other cars to drive plus the 930 is off the road in the winter so the fab and tuning work can easily be taken care of.

Rob,
I'll see when i can make it down. Storage insurance goes on the car as of the 13th of this month.
I'm running those same Siemens 60lb/hr injectors in my Ford Focus!

Geoffrey

Mapping ITBs on N/A engines is very easy if you use TPS as the measure of load for the main fuel table. There are some other things you need to do for altitude correction but that isn't a big deal.

Are you suggesting installing ITBs before your custom made intake plenum? If so, I'm not sure what that would buy you over a large single throttle body. I would think you'd loose any advantage of ITBs which has to do with velocity and flow for the particular cylinder the ITB is on.

Geoffrey

Dean,

Are you running a narrow band sensor or a wide band sensor connected to the DTA. Without knowing your specific situation, I would offer the following observations: If you have the main fuel tables and correction tables properly tuned, you should not need any type of closed loop fuel correction from an O2 sensor. Because of the low compression, the engine does not like to idle at 14.7:1 AFR since the air velocity is low and the VE is also low at idle. So, if you have a narrow band O2 sensor it will try to correct it to 14.7:1, that is the only thing that type of O2 sensor can do. If you have a wide band sensor, then you'll also have a lambda target table, so if the DTA unit is leaning out your engine, I would think that either the target table isn't reflective of what your engine needs to run at or your base fuel table is not correct.

ZX3tuning

no, i'm talking about using the ITBs as you would for a normal N/A setup but then using curved trumpets into a plenum shared by both banks.
I figure running a 4" tube cut in half and boxed out into an oval with a 4x8 diameter or there abouts, have yet to really sit down and do the math on it, will provide enough internal volume to support the required CFM needed by the engine. the curved trumpets extending into the plenum would also maintain a smooth flow of air into each cylinder and also increase velocity into the ports.
in reality, this would not be much different than running a standard EFI Plenum style IM, the only major difference would be that i'm running ITBs rather than a big single or dual TB system.

I have seen this done with great success on many cars both NA and boosted. the older M5 comes to mind of a ITB setup into a shared plenum.

doing this i could run a MAP and MAF system for extremely accurate fuel metering based on load and also that will self correct for altitude in most situations... with a MAF system, i can run a Blow-thru setup and later easily convert to a TT setup without having to change much on the IM setup if at all. plus i can also run a couple of big BOVs that would further increase the responce of the entire system.

like i said, this is no more than an idea at this point. I can easily build it and have done similar things for other cars, i just need to know the practical application of such an idea onto the 930.
the tuning i can also handle on my own for the most part, i may have some 930 specific questions when it comes to scaling the tables correctly.

by the sounds of it nobody has done such a thing yet with one of these cars...

Oh and i was planning on using the JenVey ITB system...

schnele

Bob Holcombe, Neil Harvey, John Truman, Stephen Kaspar and Steve Weiner all told me as I was considering ITBs for my Turbo, that it can and has been done but is problematic and not recommended for a street application.

Geoffrey

"doing this i could run a MAP and MAF system for extremely accurate fuel metering based on load and also that will self correct for altitude in most situations... "

You'll have the same difficulties running MAP with the setup you propose, in fact, taking vaccum/boost from a common plenum "before" the throttle bodies as you suggest is not really manifold pressure. Manifold pressure comes from below the throttlebodies. I think you can run MAF easily enough, but I don't think that is the best way to meter fuel on a performance engine.

The 993RSR engine is similar to what you propose, with 6 50mm throttle bodies connected by a shared "intake" system and I use the word "intake" loosely. This actually provided for some additional low end torque on these engines.

ZX3tuning

well like i said, it's strictly an idea at this point, i'm just looking for idea's to help develope the idea.
if worse comes to worse i can always remove the butterflys from the ITBs and convert to a big single TB. i can build it into the design so i just have to unbolt the inlet to the plenum and replace it with a TB...

125shifter

poorb0yw built a twin turbo with ITB's. A search on Pelican and Rennlist should turn up some info or you could PM him. I know he had some trouble with the linkage and getting it to idle, but I don't know how much of that was caused by the ITB's being under boost part of the time.

DeanM

I am running a wide band O2 sensor.

Again maybe it is me and my lack of tuning skills but it seems to me that I have my target tables set up correctly. For example I have my wide open throttle set up for 12 to 1. When I read my logs my motor is running 13 to 1 and the ECU wants me to take out more fuel. Uhhhh I don't think so.

I have talked with 2 people who know DTA better than me. One said "oh yea we just set the target richer than we need." The other said " there must be something in the algorithum of the program that is ****ing up the works."

What ever. I am still going to try some more settings to make it work.

Dean

ZX3tuning

what inputs are you using to setup the tables?
have you double checked that all the numbers are correct and your wideband is in fact calibrated correctly?

DeanM

Hi Mitch,

I don't know what you mean by inputs.

I have checked the O2 meter readout vs what the ECU is seeing and the #'s are the same. So I think it is calibrated correctly.

Dean

A.Wayne

I would have to disagree with this !
Wrong info in , wrong info out. the lambda function does require proper knowledge of the setup on any system to function correctly in closed loop . unless the System was supplied with a wideband lambda package with built in parameters.

Setup accuracy is affected by ,
1. Lambda sensor Location
2. PID values
3 Max inc/decrease
4. target value in relation to Injector cutoff
5. target values in relation to engine requirements vs Pressure vs Rpm vs temp
vs Fuel pressure .

6, Type of injectors ( injector type and size determines lowest A/F possible before instability occurs. Fuel drop out)

Now if fuel drop out occurs at idle while trying for a 14.7 mixture all lambda sensors will read this as a rich condition and will try have the ecu lean out
the mixture . This will show as an irratic swinging of the mixture amt . this instability is the first sign you do not have the system setup correctly, and will require the correct parameters and knowhow to get this done. when done correctly it works as stated ..

NineMeister

Intake design is never simple....

The optimum intake port profile for a performance engine would have a completely straight centreline from the throat of the air horn to the back of the intake valve, any curve in this centreline will cause flow losses. The ideal internal profile would also be tapered, in simple terms the taper would accelerate the air speed towards the valve and increase the density of the charge on the way into the engine. That said, in 95% of turbo applications running parallel walled curved ports would not matter, because you simply increase the work of the turbo to overcome the losses, however IF you intend to push your engine to the very edge of its performance envelope these losses will be a factor in limiting its performance. For my money starting with ITB's and topping them with curved runners is a mistake, it would be better to have individual plenums over each bank linked with a crosstube, the air feeding the centre of the tube from the intercooler.

The second mistake often seen is having the individual air horns "merge" into the bottom face of the plenum, which is easy for manufacture and looks pretty, but it is not optimum. A good air horn will have a fully rolled edge (imagine a donut sliced across its diameter) and these horns pull most of their air from below the top face. Hence the most efficient plenum design would have the horn lifted above the floor of the plenum, where space is an issue you can even have the horn within 30% of its max diameter away from the roof before it has an impact on flow.

Whlst on the subject of plenums, flat or regular curved walls are to be avoided as they induce resonant waves within the assembly, and unless you have access to expensive engine modelling programs it is more likely that the resonances in the system would be detrimental to the performance. The size of a combined plenum should also be considered, in this case I am assuming that you do not have to run a restrictor for racing, therefore the volume of the set up is not that critical, although I would err towards the large size to give the engine a larger reservoir of pressurised (boosted) air to breathe. If you get all the above right for the engine and run the ITB's close to the head, the key advantage is that a turbocharged engine will respond quicker to throttle because it is storing the boost pressure closer to the cylinder.

After saying all that, in the case of your engine I would just be honest with yourself and question how much power you are likely to want/afford, and if you can afford and want the ultimate the ITBs are a worthwhile investment in time and energy. However if a stock 964 intake manifold will give the 600hp & 750Nm that the engine can make, why bother?

Raceboy

I fabricated an ITB manifold for my 931. Though it's not 911 I thought you guys might be interested in looking it.
It's in non-completed form in those pics but you'll get the idea. Damn, I have to take updated pics...