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Assuming an upgraded fuel system, turbo, and external boost control :innocent: ....how much boost do you think my motor can take.... safely and constantly?

Everyone talks about the 2.24 MAP and the OEM turbo, but neither of those apply in my case.

Just curious.


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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Upgrade today to remove Google ads and support TLF.

I have no scientific data to back this up but I routinely ran 1.2 bar on my S4s with the stock internals and head and upgraded injectors. This was after a rebuild due

to a blown head gasket. The head gasket failed because of a faulty wastegate allowing overboost of around 1.6 bar and a teenage son without enough sense to read a boost gauge... :wallbash:


1995 S4s

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Cool. It looks like I'm kissing 1.25 at 4500 and then tapering off to 1.0 at read line.

How were you controlling boost? How do you know it failed at 1.6?

Thanks Jim.


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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Well Lucas, my first head gasket let go at about 1.9 bar. however, this one let go at less than 1 bar. I am thinking that the engines don't like more than 1.3 or so. I suppose I'll have to keep the RX7 as the ass kicking car and the Esprit as the panty dropping car! :ice:

Artie


89 White Esprit SE

...a few little upgrades....

93 RX7.....Silverstone

....slightly modded...Muahaha...

New Addition:

1990 300ZX TT......Hmmm

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Dunno what your setup is there now Lucas but remember more boost = more heat.

Example running a std turbo past 1 bar might feel good for about 2 seconds but when he heat kicks in the turbo has to work 45% harder to maintain the boost.

This is why a lot of chipped cars are great off the line but look shit on the dyno becuase the power only lasts a few seconds before the turbo chuffs out.

I would always go efficiency over more boost, thats the Lotus way imo :)

Most poeple I know who have chipped their car need some sort of major repair in 40,000 miles

On the flip side most cars that are standard seem to last a LOT longer (the GT2 is 93,000 miles on the same head gasket and it goes like a rocket, notably faster that the GT3)

I think what ever the situation adding more boost decreases the life expectancy, IF I ever chip either of mine the most I'll goto is 1 bar - the remaining performance through efficiency.

I think the S300 Lemans cars run at about 1.4 bar at 380 horse power for the race....or along those lines as a guide.

They did have some overheating and headgasket issues too, thats within a 24hr race....


facebook = [email protected]

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Lucas,

To answer your question, I knew I had a boost control problem but had not had time to address it. I had seen 23 psi on the aftermarket boost gauge I had installed so was keeping my foot out of it until I could fix the problem.

The wife and I went on holiday for the weekend and my 18 yr old son found the hidden keys and took it for a joyride and blew the head gasket. Then he parked the car in the garage and hoped I wouldn't notice...not his brightest hour.

I made him pay for the parts for the engine rebuild along with helping me do the job.


1995 S4s

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Good Dad, bad son. Wish mine had made me rebuild an engine.


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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OK let me ask a question. The history of my car as best I can judge, someone cooked the motor at about 28,000 miles, I take this from bills for a top end rebuild and work on the cooling system.

It has now done 64,500. When I fist got it at 52,000 the compressions were everywhere, after feeding some good oil and giving some exercise they came good to 138-140 across the board. I was running the boost at 8 psi, (not done with a very accurate gauge).

After the water pump, timing belt change I seemed to loose boost down to 6 psi, about where it should be. This time with an accurate gauge I took it up to 10, can't believe the difference 2 psi makes !

So here is the question 10 psi is about .7 bar, but I want more ! so I'm going to take it up to 12 psi or .8 bar, that I believe to be reasonably safe in a car of my vintage, but if that doesn't scare me should I be cautious about going to 1 bar or just do it ? :devil:

It's all very well to say drive it on the gauge, but sometimes you can be a little busy for gauge browsing.


Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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Roger, I cant remember if you have got an electronic boost controller fitted to your motor? If you haven't then remember that the overboost switch comes in at 0.75 Bar. I think that 0.8 should be ok however I would be worried about the heat build up and pre-ignition especially if you cranked it up to a Bar.

I would want to be able to monitor everything at 0.8 if there are no other systems in place to cool the thing down.

Edited by chris

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No the only boost control is my right foot. The way I see it is under "road" conditions max boost is not for long, but I'll take advice on all aspects.


Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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Well I just put another 1 &1/2 turns on the rod, I wanted 2 but the male part in too long ( :evil: ) so if I want to go any more I'll have to cut it down some more. :devil:

I'll report back on the result.


Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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The engine can handle the boost.. but watch the AFR (minimum 12.5:1) and IAT (anymore than 160Fand your in big trouble.)

My advise.. test AFR and IAT on a road dyno before cooking your pistons..


If you set no goals you shall surely reach them..

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Chris (or anyone else in-the-know),

I am very interested in your set up...

How do you switch between "two boost levels"? What controller are you got wired, and how it works?

Thanx

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John,

Lucas has an AEM Truboost Boost controller if my memory serves me well. Electronic controllers like these have a "scramble" or HI boost function and also a "low" boost function. All electronic controllers have these separate functions to allow you to have a normal street boost feature and a "Play" boost setting. You usually have a switch on the controller that allows you to switch or toggle between these functions, however, I have a Greddy Profec B controller in my 300ZX which has a steering wheel mounted switch so I don't even break a sweat reaching for the switch when beating up on some corvette or viper that comes along.

Art


89 White Esprit SE

...a few little upgrades....

93 RX7.....Silverstone

....slightly modded...Muahaha...

New Addition:

1990 300ZX TT......Hmmm

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