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Old 03-18-2007, 02:26 PM   #1
vaj
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Default Utec,Green, 04STi.. With SD out is there a reason to use a big MAF?

Hello all,

TIA for any help. I've studied the user manual, Micks guide ptII and the boards on this one.

I'm in the process of installing a 3",8cm2, IWG FPGreen (pnp'd from FP group buy,) walbro, PE850's, APS 525 fmic, APS inlet, TGV deletes, and a new intake system. Car has headers and a 3" TBE currently.

My question pertains to the choice of intake system. I've got a 70mm APS CAI on order but I'm wondering if I should get the 65mm. Will the 70mm just create more headaches at idle/below crossover/while tuning? Obviously a big maf isn't necessary for SD...

I am new to the UTEC.. I've had other EM before but not one as flexible as the UTEC. On my car I'd like to use the SD option for fuel tuning as it seems more stable with respect to afr's (from what I've read here.) Since the MAF is only used for the IAT temp probe after crossover would it be worth it to even have an oversized MAF??? Or am I (a novice tuner) just looking for problems?

From what I understand the utec and stock injector sizes will have to be adjusted to make the larger maf work well at idle and below crossover. I take it if the calibration for the Perrin MAF and modded STi injectors would be to start the UTEC inj size at 660 and stock at 550 then the APS 70 mm intake (a wee bit smaller than the Perrin) and the PE850's (wee bit bigger) than the inj size calibration would be very similar?

Also, what I noted from a discussion, found while searching, that even though the Perrin Big MAF is ~XX% larger than the stock MAF the injector difference is roughly 22%, much less than the actual percentage difference. ( I can't remember the exact figure for XX)

Now, if the 70MM is a little smaller than the Perrin unit would the same correction factor apply to the inj diff? In other words would a difference of ~20% be correct?


So to wrap up... If I'm going to use SD would I (a novice tuner) be opening a can of worms with a Big MAF setup? Should I just stick to the 65MM APS intake and call it a day? It doesn't seem like the 70mm would be nec. if running SD fueling. Is the 70MM worth it to have for ANY other reason other than to give the maf more headroom?

Ok, sorry to be long winded but I really want to make the "right" decision for me.

TIA TIA TIA
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Last edited by vaj; 03-18-2007 at 03:10 PM.
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Old 03-19-2007, 05:06 PM   #2
vaj
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buuuumpers!

Any opinions at all?
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Old 03-19-2007, 06:33 PM   #3
Master2192
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I think I agree with your idea, If you are going SD there is no reason to go with a big MAF setup. Why make your tuning harder for very little gain?
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Old 03-20-2007, 12:10 AM   #4
vaj
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Hey thanks! I've got one "aye" on the 65mm then. The more I think about it (and the more I look at these ported TGV's on my desk) the more I think that the gains to be had will not come from a 5mm intake diameter difference. And I'm sure it will be easier to tune.

More Opinions Please!
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Old 03-20-2007, 12:39 AM   #5
Tgui
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I have no opinion on your setup, but I'll say thank you for doing your research before asking questions I plan to have a similar setup in the future. Have fun and good luck.

BTW Maf scaling is often better done via a ROM flash. Yes I help write this tool and I'm biased, but checkout Enginuity.org for some really helpful people.
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Old 03-20-2007, 02:16 AM   #6
vaj
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Yeah, search is great. My eyes bleed from the love of search. I am still searching now.

Thanks for the enginuity tip. I've got some open source programs currently and am looking into using them for inj size, TPS mapping, fuel cut (to run aftermarket MAP for SD,) etc. Searching around enginuity.org as well

Last edited by vaj; 03-20-2007 at 02:28 AM. Reason: so very tired
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Old 03-20-2007, 07:49 PM   #7
mick_the_ginge
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No need for a BigMAF if you are running SD.
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Old 03-20-2007, 08:34 PM   #8
vaj
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Thanks Mick! I was hoping you'd chime in here. Your opinion is valued.

OK, two ayes for standard size MAF.

any other UTEC masters wanna gimme your 2c?
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Old 03-21-2007, 03:19 PM   #9
vaj
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Quote:
Originally Posted by vaj View Post
The more I think about it (and the more I look at these ported TGV's on my desk) the more I think that the gains to be had will not come from a 5mm intake diameter difference.
It appears from one trusted source I've had the pleasure of PM'ng with that the 70mm will give some gains even under SD...

One Aye for the 70mm, two ayes for the 65..

Keep those opinions to.... THE BOARDS. MOARPLZ!
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Old 03-22-2007, 09:14 AM   #10
ride5000
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well, there is an advantage of a big maf whether or not you're running SD:

it is less restrictive.
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Old 03-22-2007, 03:07 PM   #11
vaj
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Thanks for your comments ride5000! More Volume = More Flow - Got it!

I'm less afraid of tuning this the more I research. 70mm vs 60 mm is not as big of a jump as a 3" maf. Tactrix cable is on the way too.

We've got a deadlocked opinion though... 2 for bigger 2 for standard.

Who's gonna tiebreak this!
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Old 03-22-2007, 03:44 PM   #12
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<<<<<I'm running SD and 8cm green EWG.

Things to consider

You won't max out the stock MAF until 4.9 volts which on pump gas and green ain't gonna happen.

At 4.9volts on the stock MAF with a green your going to be running above 22psi which max's the stock MAP sensor as its only 2.5 bar. You will need to fit a larger one and run race gas.

At 4.9volts the stock motor is reaching its reliabilty limit for a track day car daily driver at around 450 crank HP with is 4.9volts on the stock MAF

IMHO
If your car is your daily driver be happy with the stock MAF and pump gas as above that things become very costly.

MAF voltages
Quote:
Originally Posted by ride5000
here's a little table of values for mafv vs. mass. i used the equation posted by Jeff Sponaugle for the mafv translation.
mass(g/s)=3.5906*mafv^3-4.0038*mafv^2+2.2571*mafv-0.4089
the first three columns are pretty accurate. the last is a VERY rough hp estimate following the 10hp/(1lb/min) rule of thumb.
Code:
mafv	g/s	lb/min	 hp
2.00	16.81	2.22	22
2.05	18.33	2.42	24
2.10	19.93	2.64	26
2.15	21.62	2.86	29
2.20	23.41	3.10	31
2.25	25.30	3.35	33
2.30	27.29	3.61	36
2.35	29.38	3.89	39
2.40	31.58	4.18	42
2.45	33.89	4.48	45
2.50	36.31	4.80	48
2.55	38.85	5.14	51
2.60	41.50	5.49	55
2.65	44.28	5.86	59
2.70	47.17	6.24	62
2.75	50.19	6.64	66
2.80	53.34	7.06	71
2.85	56.62	7.49	75
2.90	60.04	7.94	79
2.95	63.59	8.41	84
3.00	67.27	8.90	89
3.05	71.10	9.41	94
3.10	75.08	9.93	99
3.15	79.20	10.48	105
3.20	83.47	11.04	110
3.25	87.90	11.63	116
3.30	92.47	12.23	122
3.35	97.21	12.86	129
3.40	102.11	13.51	135
3.45	107.17	14.18	142
3.50	112.39	14.87	149
3.55	117.79	15.58	156
3.60	123.35	16.32	163
3.65	129.09	17.08	171
3.70	135.01	17.86	179
3.75	141.10	18.67	187
3.80	147.38	19.50	195
3.85	153.84	20.35	204
3.90	160.49	21.23	212
3.95	167.33	22.14	221
4.00	174.36	23.07	231
4.05	181.58	24.02	240
4.10	189.01	25.01	250
4.15	196.63	26.01	260
4.20	204.46	27.05	271
4.25	212.50	28.11	281
4.30	220.74	29.20	292
4.35	229.20	30.32	303
4.40	237.87	31.47	315
4.45	246.76	32.65	326
4.50	255.86	33.85	339
4.55	265.19	35.09	351
4.60	274.75	36.35	363
4.65	284.53	37.64	376
4.70	294.54	38.97	390
4.75	304.79	40.32	403
4.80	315.27	41.71	417
4.85	325.99	43.13	431
4.90	336.95	44.58	446
4.95	348.16	46.06	461
5.00	359.61	47.58	476
5.05	371.31	49.12	491
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Old 03-22-2007, 04:51 PM   #13
vaj
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Thats great info! Thanks for that table. I'm about to dig through that thread too. I had not found that yet. Upon reading the equation and referencing this table I now see exactly what you mean. Especially good to hear from someone with a similar setup too.

As far as the DD thing goes.... No, this is not a daily driver at all. Got a truck for work lol. I do realize that ~22-23 psi is the limit of the stock MAP. I'm aware that anything past that on a green may be hazardous to my (stock internal) engine's health and I won't be going there (yet.)

I def. understand the monetary commitment thing very well. The eventual plan is to get a basic stg2-3 shortblock with pistons, bearings, balanced RA, etc. At this time the upgraded MAP will go in and the race gas will be able to be utilized. Nothing crazy really. However, this is one year away as I have just spent most of what I had for my project at this time.

In short. THANKS again for that table as it helped clear up some of my most important questions. Your search > my search. Much appreciated!!
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