High vacuum on 5L

[GTP 85]

Just thought i'd raise a point of discussion.

Have a new/er engine installed in my VN v8 for almost a year now. now up to about 130k...

Runs heaps healthy and under the rocker covers its clean as heck. so obviously well looked after.

eveytime my tuner has it on the dyno he is gobsmacked about how much vacuum the engine creates. it has caused a few issues with tuning. He said that he has to finetune certain aspects of the maps much more carefully to ensure smooth acceleration. But it still tunes up well.

He says there is nothing wrong with having a lot of vacuum in a stock internal engine. and that its just a 'healthy donk'. Yet he has never seen one like that before.

What causes this? just good comp or what?

[immortality]

good vacuum is normally a indication of a healthy, well put together combo. is it 100% stock? maybe someone has optimised the cam timing.

[ari666]

[on a carby engine] high vac could be the result of a restriction in the inlet system. pretty sure it'll be the same for efi. what kind of vac reading are we talking about? but as you say, its probably nothing to worry about.

[GTP 85]

good vacuum is normally a indication of a healthy, well put together combo. is it 100% stock? maybe someone has optimised the cam timing.

other than exhaust its a stock, low km wrecker replacement. Cost me $1k supplied. Makes plenty of grunt, so I'm happy

[immortality]

what's it putting out at the wheels?

[GTP 85]

250 hp at the wheels on a dyno dynamics. Manual, cai, twin 2.5, tuned to death

[Blown V6 Hatch]

184kw at the wheels? Come on man....no way.

[GTP 85]

184kw at the wheels? Come on man....no way.

You prefer me to say what it didnt make? whether you believe me or not i dont care, as its just a number. I can get a graph if you want me to as it wil be on file, but isnt there always argument about it being 'a tuning tool' only.

153 auto tuned, 176 with a single 2.5 catback tuned, then went a further 10kw after a twin 2.5, 200 cells cats and a tune. same dyno. Whether you think its 'happy' or not, thats the numbers it made. Its just a number!

oh, and for comparison sake... the very same day it made 176, my mates 286 cammed tuned manual VN calais made 188kw. they were tuned and run within 2 hrs of each other

[GTP 85]

The reason for this thread was to find if excess vacuum could be evidence of internal modification?

[immortality]

The reason for this thread was to find if excess vacuum could be evidence of internal modification?

it can, but normally a cam with some overlap will loose some vacuum. which is the reason for the lumpy idle like with a 286 cam.

what rpm was the peak power?

just out of curiosity, have you done a compression test? i'd be interested to see what the numbers are

i think we can say with some certainty that it's not stock, there is no way in hell a stock 165kw motor will put out 184rwkw without a decent amount of bolt on mods.being a manual will help though

[GTP 85]

it can, but normally a cam with some overlap will loose some vacuum. which is the reason for the lumpy idle like with a 286 cam.

what rpm was the peak power?

just out of curiosity, have you done a compression test? i'd be interested to see what the numbers are

i think we can say with some certainty that it's not stock, there is no way in hell a stock 165kw motor will put out 184rwkw without a decent amount of bolt on mods.being a manual will help though

I will go back and try to grab more details of the dyno run etc. Yea i might do a comp test too, now u mention it.

Oh, yea... its not totally stock! has most bolt on mods that everyone does. But i am yet to open it (internally), cause im a V6 man myself... not real interested in tinkering with 5L too much

[IBLOWN]

250FWHP me thinks.

[Cúl-Báire]

250FWHP me thinks.

Nah I reckon at the wheels is quite feasable, it is a manual and wouldnt be supprised if it's a roller block.

[GTP 85]

250FWHP me thinks.

250 fwhp would equate to barely more rwhp than a bog standard auto??? nice one

[GTP 85]

anyhow...

can anyone else provide imput into my original question? if not... ah well life goes on

[IBLOWN]

250 fwhp would equate to barely more rwhp than a bog standard auto??? nice one

Dunno where your figures come from but i havent seen too many ''stock'' 165KW 5L's pull more than about 130RWKW (174hp) X 20% = 156FWKW = 217FWHP.

Considering its done 130k the power will have a small drop.

Where does the extra 70 odd HP come from if its stock?

My wifes 5L VT SS 180KW pulled 212RWHP and its manual, stock and tuned.

[AirStrike]

Nah I reckon at the wheels is quite feasable, it is a manual and wouldnt be supprised if it's a roller block.

It's a VN, why would it be a roller?
Mine made 161rwkw with CAI, tune, full exhaust, YT platinum rockers and 98RON. I think that figure is a little high, so if you think that yours is accurate your on some good shit.

[GTP 85]

Dunno where your figures come from but i havent seen too many ''stock'' 165KW 5L's pull more than about 130RWKW (174hp) X 20% = 156FWKW = 217FWHP.

Considering its done 130k the power will have a small drop.

Where does the extra 70 odd HP come from if its stock?

My wifes 5L VT SS 180KW pulled 212RWHP and its manual, stock and tuned.

Not interested in the numbers argument, thanks. They are the numbers, and i measure the gain per mod on the same dyno. Dynos can vary, well all know that!! I dont care if your wife or uncles car make Xkw. My thread wasn't titled...

"My car makes XXXkw, please tell me how impossible that is"

Its a daily hack, do you really think i care about the power it makes? cant even use that power

The thread is a question about high vacuum!

[Cúl-Báire]

It's a VN, why would it be a roller?
Mine made 161rwkw with CAI, tune, full exhaust, YT platinum rockers and 98RON. I think that figure is a little high, so if you think that yours is accurate your on some good shit.

The OP said "Have a new/er engine installed in my VN v8 for almost a year now. now up to about 130k..." and given the list of mods, and power figure it could well be a roller.
I think we've all gone a bit OT here anyways...

[AirStrike]

The OP said "Have a new/er engine installed in my VN v8 for almost a year now. now up to about 130k..." and given the list of mods, and power figure it could well be a roller.
I think we've all gone a bit OT here anyways...

Possible, highly doubtful.

[IBLOWN]

Not interested in the numbers argument, thanks. They are the numbers, and i measure the gain per mod on the same dyno. Dynos can vary, well all know that!! I dont care if your wife or uncles car make Xkw. My thread wasn't titled...

"My car makes XXXkw, please tell me how impossible that is"

Its a daily hack, do you really think i care about the power it makes? cant even use that power

The thread is a question about high vacuum!

Ah well must be a good tune or a very happy dyno then ay.

Good luck!