Best Maximum boost pressure for a GTA Turbo ?.

You'll do well to break a UN1 with a 2.5t, but a 3 litre if pushed will.

Lotus put about the myth that they "uprated" the transmission so they could sell spares instead of Renault. They are 100% the same.

There are so few Venturi 400GTs that I don't think stats count as far as failures go. The 400 Trophy has a different gearset and dog engagement.

According to Kevin Jones, the man who makes those uprated gearsets and single piece inputs: 300hp/300ft-lbs is about your limit.

[quote=]
Q..... So if the GTA Turbo runs at 0.85bar standard. Why do people need to remove the cut-out limiter ?. As Lee has already said it is unlikely anyone will ever run over 1bar.[/quote]

Paul, if you get any boost spike, or tweaked up so that a boost surge causes the MAP sensor output to saturate on the 5Vdc reference voltage, the ECU cuts the fuel injection until the revs drop substantially - you experience the brick wall and loose all power, not so great. It's not a soft cut, more a complete starvation. Hence, the mod to remove the boost cut. There are some other modifications to reduce ignition advance cut, the critical sensors are all PTC temp coeff. and poor electrical connections will rob power directly. Word to the wise – check your air and water temp sensor connections and loom wires right back to the ecu, we are talking some very old terminations now…

[stephendell]

Gearbox is one thing but the drive shafts aren't indestructible either . A610 drive shafts have bigger joints but are otherwise interchangeable, but Simon Auto's want a lot for them.
Mr Dell was working on a lower cost solution there...I must get my spare A610 shafts off to his specialist sometime for copying.

Yes please!

BTW when I was at the factory they confirmed it was the driveshafts that were the weak link when moving from GTA bhp to A610 bhp not the gearbox, although allegedly that is modded too

[quote=]
Q..... So if the GTA Turbo runs at 0.85bar standard. Why do people need to remove the cut-out limiter ?. As Lee has already said it is unlikely anyone will ever run over 1bar.

Paul, if you get any boost spike, or tweaked up so that a boost surge causes the MAP sensor output to saturate on the 5Vdc reference voltage, the ECU cuts the fuel injection until the revs drop substantially - you experience the brick wall and loose all power, not so great. It's not a soft cut, more a complete starvation. Hence, the mod to remove the boost cut. There are some other modifications to reduce ignition advance cut, the critical sensors are all PTC temp coeff. and poor electrical connections will rob power directly. Word to the wise – check your air and water temp sensor connections and loom wires right back to the ecu, we are talking some very old terminations now…[/quote]

In line with your recomendations... Today i have been cleaning every electrical connection i can lay my hands on. Removed the tub in front and cleaned those all under there. Removed every single electrical plug / connector under the engine bay. Right down to the Injector plugs. Plus all connections i could get to under the car as well.
I went through 2 cans of quality Switch / Contact cleaner / lubricant. (Servisol Super 10).

Again, another job well done. And now my Oil Level Gauge works !!. Bargain.
Afterwards i took the car out for a drive, and brought it up to full running temp.
Came back home and connected up the CO meter which had been running for over an hour warming up.
The car is showing 1.23% CO at idle.

Didnt even need adjustment. Perfect

Good stuff

Hi all,

My GTA has the Renix ECU upgrade, and supposedly has uprated boost pressure. Allthough it did not seem any different from other GTA's i had driven.

Paul, which Renix ECU upgrades are you referring? Can you please check and let me know. If it's the old buffered (op-amp) pot board (usually fitted on connectors bodged inside the ecu, but equally could be fitted externally), throw it away! It does more harm than good. I did explain this on another thread that phantom disappeared. But to explain, the bodge board changes the slope of the output of the map sensor so that it doesn’t hit the above mentioned reference voltage. Hence, it reduces the gain effectively (y=mx+c), and so for any actual pressure point the ecu thinks it’s seeing a lower actual pressure, and consequently cuts back the injection duty cycle – reduces the fuelling directly, not exactly what you want when you are most likely increasing the boost pressure. The fudge to this is then increasing the overall fuel rail pressure by fitting an adjustable regulator…. So the mess goes on… If you have one of those fitted, then I strongly suggest you take it off, and go back to std fuel rail regulator as well. There are better solutions, and just for ref there are some others that are supposed to be remaps, and they aren’t. Brodie Britain Racing (BBR) did a chip many years in the past, not too many floating around now, but fuelling isn’t ideal – two versions, and there have been some more recent ones. So it’s worth knowing what you have fitted exactly.

On the gearbox stuff... there are a couple of differences between the UN gearbox in the A610 and the GTA, a part from slight changes in the ratios if I remember right. But the principal is the differential in the 610 is a 4 spider and not a 2 spider as in the GTA. You can get a 4-spider diff out of one of the other UN gearboxes in the series, possibly the UN5. Certainly the 21 and GTA turbo have a 2 spider and these will break.

The other difference is the top shaft has been changed so that a twin Timken opposed taper bearing can be fitted. The UN1 has a twin roller bearing. However, chatting to the off-road racing nutters in Oz who use the UN1, the GTA version of the top shaft and bearing will take more abuse, where as they have broken the bearing on the UN5 gearbox that has the same rear bearing as the 610. I think it principally comes down to rigidity and flex; the original bearing can tolerate more distortion in the casing through torque and side loads etc, whereas the later design doesn't and will bind. They made some straight forward recommendations to me - very good oil, some mods to the internal mech setup -not easily repeated here, 4 spider, and not using the gearbox for engine breaking (if giving it some)... well I guess crashing down mountains and ditches and stuff... but otherwise they seem to get along ok. Everything has it's torque limit. 5th gear is terrible, and so just a shopping gear for those of you pushing power levels higher. Probably wouldn't have been so bad if the actual machining had been better, most of the broken ones I have seen, the gun drilling for the oil feed has not been central to the shaft, and so leaving a very thin wall thickness on one side... so not giving it a chance, and yes it will snap sooner. So if Lotus were doing inspection, I bet they were looking at this particular point, and possibly changing the sleeve coupler (it's only EN24). Made some a few years back, but we would need to do a group buy if people were really interested as it wasn’t cheap.

Good stuff

Paul, which Renix ECU upgrades are you referring? Can you please check and let me know. If it's the old buffered (op-amp) pot board (usually fitted on connectors bodged inside the ecu, but equally could be fitted externally), throw it away! It does more harm than good. I did explain this on another thread that phantom disappeared. But to explain, the bodge board changes the slope of the output of the map sensor so that it doesn’t hit the above mentioned reference voltage. Hence, it reduces the gain effectively (y=mx+c), and so for any actual pressure point the ecu thinks it’s seeing a lower actual pressure, and consequently cuts back the injection duty cycle – reduces the fuelling directly, not exactly what you want when you are most likely increasing the boost pressure. The fudge to this is then increasing the overall fuel rail pressure by fitting an adjustable regulator…. So the mess goes on… If you have one of those fitted, then I strongly suggest you take it off, and go back to std fuel rail regulator as well. There are better solutions, and just for ref there are some others that are supposed to be remaps, and they aren’t. Brodie Britain Racing (BBR) did a chip many years in the past, not too many floating around now, but fuelling isn’t ideal – two versions, and there have been some more recent ones. So it’s worth knowing what you have fitted exactly.

Interesting stuff !.
I have no idea what exactly has been done. Only that it has an ECU upgrade. This is mentioned on one of the ancient invoices from the cars early days.
Well i got alot done today, so all i have to do tomorrow is wash the car... So when im done, i will disconnect the battery, and remove the ECU.
Then split, and take some Photo's.
Like you say, it would be good to know.

On another note... After cleaning all my connections today, and Cleaning main Earth points. My oil pressure gauge is going to the end of the scale. "6", once over 2000rpm.
I assume 6 means 60psi ?.

Cheers,

Uprated input shaft coupler:

http://www.delorean-parts.com/Merchant2 ... gory_Code=

Excellent, apart from the : "Sorry, we are currently sold out of '"bulletproof" transmission coupler'. Please check back later."

About the right price GBP=USD when you take into the pound at the moment and tax etc...

May be I should get a few more made, only got my original proto left

He'll make one to order, they don't keep stock.

Hi Paul, 1 bar pressure = 15psi approx.

6 bar = 90psi

I would get a calibrated oil pressure gauge onto the engine and check it.

If its to high the pressure relief valve could be sticking.

Too high oil pressure is as bad as too low an oil pressure.

I don't think the std gauge is to be believed ...It's sort of like .....yeh ..but this one goes up to 11 man .....

Well today i gave my boost pressure a little tweak on the bleed valve that has been previously fitted.
In the last few weeks i have been getting 0.6 to 0.7 bar under full power.
So gave it alittle tweak, went out and tested, came back, another tweak and so on.

Now i have a solid 0.85 bar in all gears. (12.3 psi).
This is the max pressure indicated in the Alpine manual. 0.8 bar +/- 0.5 bar.

OMG
What a difference, it goes like a scalded cat !. Geez. 2nd gear is over in a flash.
Thats quite enough boost pressure for me. Cannot see any need to go more than standard. I dont have the balls. lol

Trust me paul you will get used to the power after a while I always do, I had an audi rs4 which started life with 380 bhp when i sold it she had a whopping 550bhp. There is always room for a little more!!

I know, ive been there too....

Had a 1997 Saab 9000 Aero. 225hp standard. Sold it with 330hp.

Also had a 1987 Chevrolet Camaro Z28 IROC-Z 5.7 TPI. 245hp standard, Sold with 511hp, and a 125hp shot of wet nitrous. It would leave black rubber on the motorway at 70 !.
But im older now, and reactions somewhat slower......