[Mk2] [Turbo] Mr2 boost vs renault 5gt turbo boost.........Question?

[blueorb]

Strange question maybe, but I have always liked the Renault 5 GT turbo, however never been brave enough to buy one given their reliabilty problems and my poor grasp of mechanics. I have also been bitten by renaults in the past!

However, I am bemused as to why 5 turbos are capable of running crazy amounts of boost, say up to 20psi with little more than an uprated head gasket. (Or at least that is how it appears with many cars advertised)

The Mr2 has to be a superior engine in terms of technology and build quality, yet we are warned off increasing the boost beyond 15psi, even with uprated intercoolers, water injection systems etc.....

So why can the Renault run that much boost (20psi) yet the Mr2 can't?

[matt_mr2t]

Why do you think there are reliability issues lol - the chavvy kids wack the boost up and boom!!

I nicely maintained R5 turbo with sensible boost wont just go wrong all the time end of.

One reason not to do it on an MR2 - the turbo's are ceramic and wont like that much abuse!

[SWMark]

Eh? I was told i can run 17/18PSi with just an uprated IC, then up to 20-22 with better management and fuelling , is this not right?

[blueorb]

Eh? I was told i can run 17/18PSi with just an uprated IC, then up to 20-22 with better management and fuelling , is this not right?

Everyone seems to get a bit nervous recomending anything over 15 psi standard, unless you start mapping, intercooler etc........££££££ etc..

But why can the renault run 20 psi without such expensive mods on an old over head valve type engine?

[MotionMan]

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[TUBBY-DEUCE]

i had a renault 5gtt i had two actually back in the day, i can safely say the engines are bullet proof, there just a bit over engineered i think, pretty amazing really that something with a 1.4 engine can go that quick, its the same with all turbo cars i guess you get the odd person that abuses them , whacks the boost up then before you know it, POP!
got alot of respect for r5gtt"s

[JAP BOY]

IF your aim of getting more power is down the route of just cranking the boost up all the time then i suggest not tuning at all.
Where as your beloved Mk2 is built as a more radical Mr2 with the 3S GTE it was also designed to give you the blast from the past everytime its designed to last. If you want more power find a different root eg: Down Pipe, Aussie Manifold, Rebuilt Hybrid, I/C or C/C , uprated actuator, EMS rouge does these at a gd price, cams, porting and polishing.

In my veiw all tubbys are very quick car but they may need just abit of refinements that list above is only a few things that can be done to your engine.
R5 Gt nice for the time they came out but you never know whats going to go wrong next.

[TUBBY-DEUCE]

totally agree with you mate, i got intercooler, exhaust, filter sevice and made sure everything was tip top before i even thought about winding the boost up on my tubby, r5gtt definatelly have had there day but respect were its due, theyre under estimated little cars and true you dont get a r5gtt if you dont like getting your hands dirty, but saying that im always tinkering with the tubby, think ive gone off the subject of your topic, sorry with standard turbo on r5gtt, it wasnt recomended to go above 12psi as it would go pop

[SWMark]

Eh? I was told i can run 17/18PSi with just an uprated IC, then up to 20-22 with better management and fuelling , is this not right?

Everyone seems to get a bit nervous recomending anything over 15 psi standard, unless you start mapping, intercooler etc........££££££ etc..

But why can the renault run 20 psi without such expensive mods on an old over head valve type engine?

Are you sure you dont mean the early MR2s(rev 1s and 2s up to december 93) ? My old Maestro could take 24PSi and was fing quick, low13s at 106-108 .

[TUBBY-DEUCE]

18psi on rev3 and above standard turbo isnt it 14psi on rev1-2 thats what i thought, but its purely down to the turbos, am i thinking right

[dai21t]

I used to have a Renault 21 turbo, I ran 22psi on it for about 5 years and never blew the engine. It was completely standard internally, just bolt on mods, hybrid, exhaust, front mount intercooler and modified ecu. It gave 221bhp @wheels and 302lb/ft torque. Was very quick, especially when I ran nitrous on it as well. Did a 13.6 @ 109mph 1/4 but struggled with traction until 4th gear. Got fed up eventually with the reknowned French build quality and sold it when it wouldn't stop falling apart around me!

[^Trickster^]

Theres alot more to making power than the amount of boost you run. Sometimes running more boost can result in less power. Its about how much air the turbo can shift at a given pressure. Its CFM that matters when tuning an engine.

I ran 16-17psi on a gen 2 totally stock engine, and for about 3 months I pulled off the wastegate pipe and just let it spike to 20-22psi and it would drop down higher up in the revs and it didnt perform an better than running the 16-17psi.

As you increase the pressure, you increase the heat, therefore you need better methods of cooling the intake charge. Bigger intercooler, or move to a larger turbo with less boost.

You need to determine the power level your going for and choose a turbo for that application, alot of people just whack on a big turbo and usually spend more money than they need to and actually sacrifice some low end power too.

I run 22psi at the moment and will be running 26psi when I get round to doing a few more alterations to my setup. But that is where my turbos efficiency is at its maximum, running higher boost would be a wste of time, then it would be time to change to a different turbo.

The engine should be designed and balanced in harmony, or you end up with bits too big and bits too small, and a real mess.

Renault 5 GT turbo are not a bad engine really, I wouldnt have one myself, but people expect too much of them for too little.

Graeme

[TUBBY-DEUCE]

Renault 5 GT turbo are not a bad engine really, I wouldnt have one myself, but people expect too much of them for too little.

Graeme

i agree,for an old push rod engine with basically a turbo bolted on engines are top for what they are, its just the craap buid quality that surrounds them

[matt_mr2t]

Greame said something I forgot to mention last night. Due to the design of the twin entry CT series turbo's heat build up at higher boost is a massive issue.

So you have two major problems with just cranking the boost up. Ceramic turbo internals likely to break and high inlet temps causing nasty detonation which could result in piston failure.

People on here who say you simply cant turn the boost up are saying because they are sensible. It wont definately result in failure but it probably will.

The R5's have weak head gaskets iirc and is the weak link on those engines. But being a push rod engine taking the head off and changing it is a much much easier job than the MR2 DOHC set up.

[The Morris]

i had a R5 GTT.

As soon as it came out the garage it went back in. Total waste of money

[matt_mr2t]

I used to have a Clio 16v before the MR2 and I was just about to get the GTT Engine Conversion done then changed my mind and bought the MR2 instead.

250bhp is a highly tuned R5 and likely to lead to all sorts of problems. 250bhp in an MR2 isnt far from standard and will run happily all day every day (and start when warm )