How much boost is too much?

[Unholy707]

2015 stock long block. 2.69 upper on a max effort ported 2018 2.4 IHI, full race bearing rebuild (snout and bearing plate). I’m contemplating adding a 10% lower with the 2.69 upper. Is this too much boost? Too much rpm for the blower rotors? Are the rotors limited by bearings for rpm?

 

[Forgedrod]

8.9/2.69 x6400rpm=21,174. Stock with 3.35 upper ~ 15,600 at 6400 rpm engine speed. Pushing the limit imho.

 

[vortecd]

SDG has a graph it is on the site for rpm

 

[vortecd]

 

[GNBRETT]

2.4's can be spun to the moon.

 

[Unholy707]

2.4's can be spun to the moon.

But how far is the moon? 😆

 

[jonx96]

in the name of science I’ll be spinning one harder then that

 

[Unholy707]

in the name of science I’ll be spinning one harder then that

On a 2.4, stock long block?

 

[Unholy707]

This will be for 9.6 seconds or less (hopefully) with cooldown time in between. Car has a chiller, e85

 

[jonx96]

On a 2.4, stock long block?

You asked about blower speed. But as far as being stock to many factors going into it. Sure you can. But the more you push the more potential for failure

 

[45-70govt]

But how far is the moon? 😆

The distance varies, but generally around 238,000 miles.

 

[BULL]

When a rod puts an inspection window in the block, that was 1lb too much.

 

[jonx96]

My rod disengaged when I went a few pounds to much 😂

 

[Unholy707]

My rod disengaged when I went a few pounds to much 😂

So I have a 2.69 on there now. Kong is doing a full port and race bearing rebuild. 108mm throttle body, and long tubes are inbound. Car has a chiller. Wondering if I’ll lose power without pulleying down a bit more, and what I can realistically pulley down to in the “safe” male rotor rpm range

 

[fubar569]

You will not lose any power.

Blower, snout, 108mm alone should pick you up 50-80hp and gain 1.5psi give or take...which is fine because you'll lose it all with the headers anyway (and gain a few more hp there too).

I have all of that and run a 2.50 pulley on stock lower at the track. It'll be alright. Til it ain't.

Edit: before the long tubes/solo exhaust I had factory manifolds with AFe mids and factory exhaust. On a cool night I'd spin to 21-22psi max on the 2.50 pulley. Lol

 

[Unholy707]

I’m pushing 18-19 now stock snout /bearing plate/ throttle body( 2018 blower)

 

[Unholy707]

I’m thinking maybe a 2.57 upper then (maybe) and leave it. Or a 2.65

 

[fubar569]

I want to say my peak this year was 20.5psi on a 2.50 - I lost a solid 1psi overall going to LT's and catback all else being equal year to year. You'll gain 1-2 from the porting & 108 and lose some of it back with the exhaust.

You should be in the same ballpark. If you have the fuel you can pulley down just a hair more and get away with it.

 

[Unholy707]

I have so much of the car apart right now I’d put a cam in if I didn’t have to do springs and pull the heads. Didn’t realize until recently if just doing the cam you can undo the rockers, spin the cam a few times and push the lifters back into the treys

 

[Unholy707]

I really need to figure out how the heck to recycle coolant