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Discussion Starter · #1 ·
Hi, guys. New to the site, looking for a little info. I got my 2G MX-6 in the shop getting a new KLDE which I plan on boosting. Anyone know off the top of their heads how much boost the stock motor can push safely?

thanks in advance
 

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with Megasquirt and a decent tune 9psi, this is probably including Milli S injectors and a larger fuel pump
 

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"Safely" is a relative word depending on the age of parts in your motor. The weakest parts always fail first.

Generally, most people run 7-8psi on a well maintained stock KLDE. If you go much higher than that you will tend to melt pistons and break connecting rods.
 

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4-5 psi Id say is the good safe, long term daily driving bet.
Go up higher and you start breaking stuff and having problems.
I definately agree with King here. Boost is addicting and you'll want more, then turn it up to 8-10 psi, drive it around like that, something breaks, you end up upgrading your pistons/rods/building custom IM/bigger injectors/MS or standalone... :D And that is before you get to start your fun with gearbox problems. I obviously haven't gotten that far yet, I've had 10psi on T4 turbo on stock internals with custom IM and extra injectors. This setup did net me 290whp and burnt valves after some time of having fun. That is when my setup started to come more as a work than hobby.

Just make sure what you want. After scaring you out, I must say, boost and KL is very nice to have, even on daily basis. :) Don't be scared away, just make sure you understand what you are getting into.

Mici
 

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yeah id say 4-5 is a good safe point. What im doing right now is running 6 psi but after a while im gonna change the spring in my wastegate to a 4 psi spring and get a boost controller to turn it up when i want to.
 

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7 psi is about max on the millenia S injectors so anything after that your going to need a engine management to control the new injectors.

I would just get a FMU and Mil S injectors and boost 5-7 PSI
 

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Discussion Starter · #9 ·
Thanks for the input guys. I'll probably boost 5psi for daily driving and turn it up to 7-8 at the strip. I'm definately going to be rebuilding the motor eventually (new pistons, rods, valves), and I am a firm believer in the philosophy of "if it breaks, upgrade it" (hence my fidanza flywheel and performance clutch) but I really don't want to risk cracking the block or any other game ending incident.

Thanks again guys, as soon as my MX hits the streets again I'll have to post some pics of it. She aint in the best condition, but she's pretty quick.
 

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Shit ay I always thought it was 12psi for the DE. I guess it is good that we stopped at 9psi. 8-9psi is still pretty stupidly fast in a fwd car with unequal driveshafts (stupid =fun also btw :))
 

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i dont understand why you guys throw psi around like it means something. you state the pressure but fail to state what turbo is making that pressure, and should be more worried about flow then pressure.

i had built an ls-vtec turbo, had 10.2:1 comp ratio on cast pistons and stock rods with arp rod bolts arp head studs and an ebay turbo kit making 360 - 370whp at 15 psi, with the ebay t3/t40e 50 trim, same one in that kit the one guy posted for the v6. use a function7 oil restrictor.

you guys should learn the hp and tq limits of the stock engine and go with that, not psi. like a stock 1.8 non vtec engine is limited to around 335 - 350 hp before thing start to break... i have a friend with an integra running the stock engine with a turbonetics t3/t4 50 trim pushing 15psi making about 320whp.

cuz 15 psi on a t25 turbo probably wouldn't make 250whp on a klde.

you guys understand what i'm saying?
 

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We are making the assumption that whoever is asking has sized the turbo properly for the car. Assuming everything is sized right, then as chef stated the 7PSI mark will probably make under 300whp which is safe. Anything over 300 and people have seen bent rods.

90% of the people are using a T3/T4 setup regardless of trim they are all going to flow in the same ballpark.

Now if your using a full T3 or a full T4 that might fudge the numbers a bit but until you jump to a turbo the size that radar is running I think it is safe to throw PSI around as an average.
 

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so every time i see the psi numbers thrown around i should assume its for a stock klde with a t3/t4 turbo.

what if i had a t3/60-1? you still say 7 - 8 psi?
 

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No, As I stated above when your changing the size of the turbo, or amount of CFM the turbo flows the PSI is obviouslly going to be affected also.

Its just a generalized number I dont see why you are so upset? If a person actually knows what they are doing, such as yourself, they will likely disregard a post like this.

This is a generalized number for people who do not know what they are doing. They might think they can boost 15 PSI like a kid down the street with a 4 cyl, or at least they want to know if hes going to blow his motor to bits doing so.


Anyone who successfully builds a turbo mx6, by the time they are done, is going to have enough knowledge and research to know how much horsepower, fuel, and spark timing is safe for their setup. Anyone who has successfully built a turbo car should have that little firefly in their gut to get on the dyno and get it tuned to see what their setup can actually put out in real numbers.
 

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Pressure is pressure, you have a given cylinder size, and a given pressure, your going to make X amount of force which is then converted to horsepower.

The CFM of the turbo is just going to litigate how soon you get to the magic number.

Of course a t25 isnt going to make 300 whp on a KLDE, because its never going to reach 10psi. It simply cannot flow enough CFM to reach that point before the valves on the heads open.

Your comparing Honda 4 cyl motors to Mazda 6 cyl motors, Apples to oranges
 

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thats what i'm getting at. i just wanted to express my feeling cuz i just seen psi thrown all over and never heard on what turbo in alot of post on here.

also i have a 91 323 and am thinking of swaping in a klde and turboing it and needed to know how much hp the block can handle cause i was thinking of building it internally, but i hear the transmissions are weak and only hold about 300whp before a gear is shattered.
 

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Pressure is pressure, you have a given cylinder size, and a given pressure, your going to make X amount of force which is then converted to horsepower.

The CFM of the turbo is just going to litigate how soon you get to the magic number.

Of course a t25 isnt going to make 300 whp on a KLDE, because its never going to reach 10psi. It simply cannot flow enough CFM to reach that point before the valves on the heads open.

Your comparing Honda 4 cyl motors to Mazda 6 cyl motors, Apples to oranges
also this right here make no absolute sense to me.
Of course a t25 isnt going to make 300 whp on a KLDE, because its never going to reach 15psi. It simply cannot flow enough CFM to reach that point before the valves on the heads open.

you would max out a t25 at high boost quicker then you would a t3/t4. the exhaust pulses and heat will spin that turbo to 15 with in probably 3000rpm or less.

but yes it wont make 300 whp.

i was thinking, from researching frakenprobe, the i could possibly hit 300 whp with a t3/60-1 at 10 psi due to the massive flow of the turbo.
 

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Would 7psi on a supercharger setup make the same peak power as a turbo running at 7psi? Considering the motors are in the same shape and all other mods are identical.
if the turbo can spool the same power band, but all things considered the turbo wont have the parasitic loss of an engine trying to drive a supercharger.
 
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