Jenvey ITBs - COS 5 on an LS1

[bimbleuk]

I contemplating installing a set of Jenvey LS1 individual throttle bodies on an LS1.

What I'm not 100% sure of is that I will be able to successfully tune them on an LS1B 512K PCM running COS5. I know the COS5 has the TPS VE table (A0007) but I've not read any posts on the forum which covers a pure Alpha-N install. Most have been on using A0007 just to help with big cams but still retaining a single throttle body.

So for example how do I populate the table A0007 to start with? I'll have the Main VE table (B0101) populated from my current setup but will that be even remotely able to run the engine to log data. I guess I can populate A0007 as much as I can with my current setup and that may get me up and running with some (serious!) massaging.

If anyone has any input on this and especially if there's anything that would be a show stopper using the PCM I would appreciate your comments.

On the positive the car is not daily driven so I don't mind taking some time to get it right and I can use my friends rolling road to populate the harder parts of the calibration.

[bimbleuk]

Anyone? You can't all be using plastic plenums still.

[joeygc5]

I prefer the Pro-Flo over stock personally. But to your questions I have only worked on 1 ITB setup. I had to fiddle the tps VE table to get the car to idle to be shipped away. Table A0003 has to be enabled and care has to be taken to make the setup work. Once again I only played with the Harrrop setup for about 25 min to get a rough idle and to be able to load the car on a trailer for transport. Stock LS6 crate motor also, no wild cam setup.

[bimbleuk]

Thanks any feedback on working setups is appreciated. I'm pretty confident I can get the car working now so it'll be down to me to tune the car as best I can.

Main reason I went for the Jenvey is it's made locally and my distributor is only 20 miles from me not several thousand like Edelbrock/Harrop.

[bimbleuk]

So now I've read a bit more about Alpha-N tuning I think I can see a limitation in the COS5. If you were to use MAP/SD with a set of ITBs then you would most likely use it at and just off idle.

When you open the butterflies on ITBs you rapidly loose vacuum so the MAP signal becomes moot. So it would be useful to set the transition from MAP/SD to TPS VE. Unfortunately the Axxxx tables in the OCS5 have been written to work the other way round. So you can use TPS VE at idle with a lumpy cam while using the MAP/MAF sensors and a single TB.

It would have been great to have the option to try MAP at idle but I think I'm going to be limited to pure Alpha-N. At least there plenty of correction tables to help with this.

[joecar]

I think you will be ok with pure Alpha-N.

[bimbleuk]

Final question related to show stoppers.

The spark tables appear to be linked to GM.CYLAIR_DMA, GM.DYNCYLAIR.DMA & CALC.CYLAIR for the load axis and I was wondering if these parameters will still function if I completely disable the MAP input?

Working spark tables would definitely be preferably

[joecar]

CALC.CYLAIR: calculated by scantool from MAF and RPM.

GM.CYLAIR_DMA: computed by PCM from MAF.
GM.DYNCYLAIR_DMA: computed by PCM from VE.

With Alpha-N you still have VE... enable/set TPS VE and log VETABLE_DMA to see this.

[bimbleuk]

Thanks for the reply.

I've already generated a TPS VE table for my current MAF/MAP setup from a log with VETABLE_DMA enabled for practise. So it's good to know it's should still work without MAF/MAP.

I've still got a week or so to wait so I've been learning to make composite parts in prep.

[bimbleuk]

Just a quick update on this as the kit arrived about a week early

I'm fitting the Jenvey's to a mildly modified LS1 in a Mazda RX7 FD3S. So far fitment has been a bit tedious as it comes fully disassembled so it takes a while to set all the ITBs and the throttle linkages. That's 99% done now. Initially from taking some measurements from another car I thought I'd have some minor bonnet fitment issues. As it turns out it was the firewall that needed the most tweaking which also included moving the front brake line T lower down where it came through the firewall.

I had one panic when I realised that I couldn't easily mount the GM TPS and to rub it in the Jenvey throttle bodies turn the spindles in the opposite direction. However I went to my supplier and borrowed a reversible TPS and spliced it in to the loom and checked the voltages via the Flashscan. Thankfully it read 0.3V to 5.0V where I'd guessed the initial position so that's another job off the list.

I've decided I will connect each inlet runner to a vacuum pot. That way the PCM will see a map signal even if I'm not intending to do any mapping from it necessarily. I was just nervous about disabling it as so many tables in the PCM appear to rely on the map for input.

You'll notice there's no ram pipes or air boxes yet. As nothing off the shelf will fit under the bonnet I'm going to have a go at making my own.


Checking the TPS voltage.



I modified the Jenvey throttle linkage bracket to fit the Mazda cable.



Only a bit of porting required on my near stock inlet runners to get a good match.





Firewall relieved to fit the fuel rail and TPS.



Next job is the fuel lines and wiring. I'm relocating the coil packs to create more room for air boxes.